Choosing among the Samsung Galaxy S23 FE, Galaxy S21 Ultra, and OnePlus 15 comes down to how you define a flagship: a newer, fully specified phone; a big-screen camera specialist sold renewed; or a current high-spec model built around speed and endurance. I rank the OnePlus 15 first for its combination of 16GB RAM, 512GB storage, a large battery, and broad carrier compatibility. The S21 Ultra is the camera and stylus pick, while the S23 FE is a more restrained Samsung option whose renewed, AT&T-specific listing deserves careful attention.
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These options have very different ownership tradeoffs. The OnePlus offers the most generous listed hardware, but its unusually broad water-resistance claims and model details should be checked against the seller’s listing and regional version. The Samsung phones are renewed devices, so condition and battery history matter; the S23 FE is also tied to AT&T, while the S21 Ultra is listed as unlocked. I focus this guide on what the supplied specifications can establish—and where they leave a buyer needing to verify details.
Complete the kit
Key Takeaways
- The OnePlus 15 is the strongest all-around choice on listed hardware: 16GB RAM, 512GB storage, a 7,300 mAh battery, and an unlocked 5G configuration.
- The Galaxy S21 Ultra has the largest Samsung screen here at 6.8 inches, a listed 108MP main camera, up to 100x zoom, and S Pen support; it is renewed but unlocked.
- The Galaxy S23 FE pairs a 6.4-inch 120Hz OLED screen with 8GB RAM and three rear cameras, but its renewed condition and AT&T association make it less flexible.
- For buyers who keep many large files or want ample multitasking headroom, the OnePlus’s 512GB storage is a substantial step up from the 128GB in both Samsung listings.
- None of these listings establishes battery health for the renewed Samsung phones, and the OnePlus’s stated resistance ratings and regional compatibility merit seller verification before purchase.
| OnePlus 15 Unlocked Dual-SIM Smartphone, 16GB RAM, 512GB Storage, Ultra Violet |  | Best Overall | Operating system: Android 16 | Processor: Snapdragon 8 Elite Gen 5 | Memory and storage: 16GB RAM; 512GB | VIEW LATEST PRICE | See Our Full Breakdown |
| Samsung Galaxy S21 Ultra 5G, US Version, 128GB, Phantom Black – Unlocked (Renewed) |  | Best for Zoom and S Pen | Condition: Renewed | Display: 6.8-inch AMOLED | Refresh rate: 120Hz | VIEW LATEST PRICE | See Our Full Breakdown |
| Samsung Galaxy S23 FE 5G, 128GB, Graphite, AT&T (Renewed) |  | Best Smaller Samsung Option | Condition: Renewed | Carrier association: AT&T | Display: 6.4-inch OLED, 1080 × 2340, 120Hz | VIEW LATEST PRICE | See Our Full Breakdown |
| flagship Android smartphone | Display | Memory and storage | Rear cameras | Battery |
|---|---|---|---|---|
| OnePlus 15 Unlocked Dual-SIM S | 6.78-inch AMOLED, 2772 × 1272, 165Hz | 16GB RAM; 512GB | Three 50MP cameras | 7,300 mAh |
| Samsung Galaxy S21 Ultra 5G | 6.8-inch AMOLED | — | — | — |
| Samsung Galaxy S23 FE 5G | 6.4-inch OLED, 1080 × 2340, 120Hz | 8GB RAM; 128GB | Three cameras; HDR and slow motion listed | 4,500 mAh |
More Details on Our Top Picks
OnePlus 15 Unlocked Dual-SIM Smartphone, 16GB RAM, 512GB Storage, Ultra Violet
The OnePlus 15 takes the top position because its listed hardware has the fewest obvious compromises for a buyer seeking a flagship Android phone. Its 16GB of RAM and 512GB of storage give it more room for demanding apps, multitasking, photos, and downloaded media than either Samsung here, both of which list 128GB. The 7,300 mAh battery is also the largest stated capacity in this group, though capacity alone cannot guarantee a particular runtime.
Its 6.78-inch AMOLED display with a 165Hz refresh rate is larger and faster on paper than the two Samsung screens. That can make scrolling and supported games feel especially fluid, while the size is better suited to video and split-screen work than one-handed use. The three 50MP rear cameras and 32MP front camera give the listing a balanced set of resolutions, but megapixels do not settle image quality; Samsung’s S21 Ultra has the clearer stated long-zoom advantage with its up-to-100x claim.
Compared with the Galaxy S21 Ultra, the OnePlus is the more appealing choice for storage, memory, battery capacity, and broad carrier compatibility. Against the S23 FE, it is a more capable listed package, although the FE’s smaller footprint may suit some people better. The OnePlus is described as unlocked and dual-SIM, which helps buyers who change carriers or manage separate lines. I would verify the exact regional model, warranty coverage, and the listing’s unusually broad IP66, IP68, IP69, and IP19K resistance claims before buying. This is the strongest pick for buyers who want current, generous hardware, provided they are comfortable with a large phone and seller-specific details.
Pros:- 16GB RAM and 512GB storage provide the most headroom in this group.
- 7,300 mAh listed battery capacity exceeds the stated capacity of the S23 FE.
- 165Hz AMOLED display and Snapdragon 8 Elite Gen 5 processor.
- Unlocked 5G dual-SIM configuration for broad carrier flexibility.
Cons:- The 6.78-inch screen and overall class of device may feel large for one-handed use.
- The listing’s extensive resistance ratings should be verified for the exact model and region.
- Camera quality and real-world battery life cannot be determined from the listed figures alone.
Best for: Buyers who want the most memory and storage in this comparison, a large high-refresh display, a high-capacity battery, and unlocked dual-SIM flexibility.
Not ideal for: People who prefer compact phones, want a clearly established zoom-camera advantage, or need independently verified details for regional warranty and water-resistance claims before purchase.
- Operating system:Android 16
- Processor:Snapdragon 8 Elite Gen 5
- Memory and storage:16GB RAM; 512GB
- Display:6.78-inch AMOLED, 2772 × 1272, 165Hz
- Rear cameras:Three 50MP cameras
- Front camera:32MP
- Battery:7,300 mAh
- Network and SIM:Unlocked 5G; dual Nano-SIM
- Water and dust resistance:Listed as IP66, IP68, IP69, IP19K
Our verdict“I recommend the OnePlus 15 as the strongest overall flagship-style package here for buyers who value capacity, speed, battery size, and carrier choice.”
Samsung Galaxy S21 Ultra 5G, US Version, 128GB, Phantom Black – Unlocked (Renewed)
The Galaxy S21 Ultra earns its place through a combination the other two listings do not match: a 6.8-inch AMOLED screen, a stated 108MP main camera with up to 100x zoom, and S Pen support. That makes it the specialist choice for buyers who want a very large canvas and flexible framing at distance. The OnePlus has newer listed platform details and far more storage, but its supplied description does not claim the same zoom reach or stylus support.
Its 120Hz refresh rate keeps the screen in step with the S23 FE and gives the S21 Ultra a smoother feel than a standard-refresh display. At 128GB, however, it has one quarter of the OnePlus 15’s listed storage. That difference matters if you keep a large photo library or install sizable games. The phone is listed as an unlocked US version with 5G, a meaningful advantage over the S23 FE’s AT&T-specific listing for people who want carrier choice.
This is a renewed model, so the buying decision depends on more than its original flagship specification sheet. The supplied details mention possible cosmetic imperfections, and they do not state battery health or remaining software support. The same caution applies to its camera claims: a 100x maximum zoom figure communicates reach, not the detail or clarity buyers will get at that extreme. Compared with the OnePlus, the S21 Ultra is a less future-facing capacity choice; compared with the S23 FE, it is larger and has a more ambitious zoom proposition. I would choose it for those specific strengths only after confirming the seller’s condition terms and return policy.
Pros:- Large 6.8-inch AMOLED display with a 120Hz refresh rate.
- 108MP main camera and listed zoom capability up to 100x.
- S Pen support adds a note-taking and annotation option.
- Unlocked US version with 5G connectivity.
Cons:- Renewed condition may include cosmetic wear, and battery health is not specified.
- 128GB storage is much lower than the OnePlus 15’s 512GB.
- The maximum zoom figure does not describe image quality at long range.
Best for: Buyers who prioritize a large screen, long-range camera framing, S Pen compatibility, and an unlocked Samsung phone.
Not ideal for: People who want new condition, verified battery health, high storage capacity, or the most current listed processor and Android version.
- Condition:Renewed
- Display:6.8-inch AMOLED
- Refresh rate:120Hz
- Main camera:108MP
- Zoom:Up to 100x listed
- Storage:128GB
- Connectivity:5G; unlocked US version
- Stylus support:S Pen support
Our verdict“I would choose the renewed S21 Ultra when its large display, S Pen support, and zoom reach matter more than newer listed hardware or storage capacity.”
Samsung Galaxy S23 FE 5G, 128GB, Graphite, AT&T (Renewed)
The Galaxy S23 FE is the most compact option in this group by listed display size, with a 6.4-inch OLED panel rather than the 6.78-inch OnePlus or 6.8-inch S21 Ultra. It still offers a 120Hz refresh rate, so buyers do not have to accept a basic screen experience to get a more manageable footprint. This makes it the Samsung I would consider for everyday use when a giant display and the S21 Ultra’s reach are unnecessary.
Its triple rear camera system gives it more flexibility than a single-camera setup, and the listing calls out HDR and slow-motion modes. The specifications do not provide sensor resolutions, so I would not rank its camera ahead of the S21 Ultra’s explicit 108MP main camera or claim image quality that is not documented. With 8GB RAM and 128GB storage, it is also less spacious than the OnePlus 15, which doubles the RAM and offers four times the storage.
The largest practical caveat is the listing itself: this S23 FE is renewed and associated with AT&T. Buyers should check that the device is compatible with their service and confirm whether it is locked, since the supplied details do not label it unlocked. Renewed condition can also mean signs of prior use, and battery condition is not provided. Compared with the unlocked S21 Ultra, the S23 FE gives up the stated zoom and stylus strengths; compared with the OnePlus, it has less memory and storage but a smaller screen. I see it as a fit-first Samsung pick, not the leading choice for buyers chasing the most ambitious flagship hardware.
Pros:- 6.4-inch OLED display is the smallest listed screen in the group.
- 120Hz refresh rate and 5G connectivity.
- Three rear cameras with HDR and slow-motion modes listed.
- 8GB RAM and fingerprint recognition.
Cons:- Renewed condition may show prior use, with battery health unspecified.
- AT&T association makes carrier compatibility a key check before purchase.
- 128GB storage is limited beside the OnePlus 15’s 512GB.
Best for: Buyers who want a comparatively smaller Samsung phone with a 120Hz OLED display, 5G, and three rear cameras, and who can use the AT&T-associated device.
Not ideal for: People who need an unlocked phone, abundant storage, a documented battery condition, or the most advanced camera and processor specifications in this comparison.
- Condition:Renewed
- Carrier association:AT&T
- Display:6.4-inch OLED, 1080 × 2340, 120Hz
- Memory and storage:8GB RAM; 128GB
- Rear cameras:Three cameras; HDR and slow motion listed
- Video capture:1080p at 60 fps
- Battery:4,500 mAh
- Connectivity:5G and Wi-Fi
- Biometrics and durability:Fingerprint recognition; water resistant
Our verdict“I recommend the S23 FE for buyers who want a smaller Samsung screen and can confirm the renewed phone’s condition and AT&T compatibility.”
How We Picked
I compared the three phones against the promise of a flagship Android smartphone: strong everyday performance, a capable display, useful camera hardware, and enough practical flexibility to suit a demanding buyer. The supplied specifications make the OnePlus 15 the most complete on paper, particularly for memory, storage, battery capacity, and carrier choice. That is why it earns the overall spot, though buyers should confirm the exact model and protection claims for their region.
I gave the Samsung models distinct roles rather than treating them as interchangeable alternatives. The Galaxy S21 Ultra stands out for its large AMOLED display, 108MP main camera, long-range zoom claim, and S Pen support. Its age and renewed condition temper the recommendation, and the listing does not establish battery health. The Galaxy S23 FE offers a smaller 6.4-inch OLED display and a modern 120Hz refresh rate, but its 128GB capacity, renewed status, and AT&T connection make it the more constrained pick.
I also weighed the gaps in the supplied information. No battery endurance estimate is given for either renewed Samsung, and the OnePlus listing’s extensive IP rating string is unusual enough that I would verify it with the seller or manufacturer documentation. I did not infer unlisted features, software support periods, camera performance, or condition guarantees. The rankings reflect the specifications and caveats provided, with carrier flexibility, usable capacity, display size, and purchase condition all affecting where each phone fits.
| flagship Android smartphone | Rear cameras |
|---|---|
| OnePlus 15 Unlocked Dual-SIM S | Three 50MP cameras |
| Samsung Galaxy S21 Ultra 5G | — |
| Samsung Galaxy S23 FE 5G | Three cameras; HDR and slow motion listed |
Factors to Consider When Choosing Best Flagship Android Smartphones
A flagship purchase is a balance between hardware, ownership details, and the kind of phone you want to carry each day. I would decide first whether screen size, camera reach, capacity, or carrier freedom is the priority, then check condition and compatibility before comparing smaller specification differences.
Start with size and screen use
The listed screens span from 6.4 inches on the S23 FE to 6.78 inches on the OnePlus and 6.8 inches on the S21 Ultra. Those numbers help set expectations: the smaller Samsung is the more plausible fit for a buyer who wants easier handling, while the two larger displays suit video, games, reading, and side-by-side work. The OnePlus lists 165Hz, compared with 120Hz on both Samsungs, but refresh rate is only one part of the viewing experience. If comfort and pocketability matter, do not assume the highest number makes the best screen for you.
Match the camera to what you shoot
The clearest camera distinction in the supplied details is the S21 Ultra’s 108MP main camera and up-to-100x zoom claim. That makes it the obvious option to investigate for distant subjects and flexible framing. The OnePlus lists three 50MP rear cameras, suggesting a multi-camera approach, while the S23 FE also has three rear cameras but no sensor resolution details in the provided specifications. I would compare actual sample images from the exact model before judging quality. Very high zoom figures describe maximum reach and do not promise clean detail at every setting.
Think about storage and workload
The OnePlus 15 is the straightforward pick for buyers who install many games, save offline media, or keep large photo and video libraries: its 512GB storage and 16GB RAM lead this comparison. Both Samsung listings offer 128GB, and the S23 FE lists 8GB RAM. Your needs matter more than the largest spec. A buyer who mainly streams media and uses common apps may have little need for 512GB, while a heavy user could find 128GB restrictive over time. Check whether the phone supports the storage expansion method you need; no such support is established in the supplied details.
Check condition and battery details
Both Samsung phones are explicitly listed as renewed. That can make an older flagship more accessible, but it also means condition, included accessories, return terms, and battery health deserve attention. The S21 Ultra listing warns of possible cosmetic imperfections, and neither Samsung listing gives a battery health measure. The OnePlus is listed with a one-year manufacturer warranty, but buyers should confirm that the warranty applies to their region and seller. For any model, request clear terms for defects and returns before committing.
Confirm network and regional fit
The S21 Ultra is listed as an unlocked US version, and the OnePlus is described as unlocked for all carriers with dual SIM. The S23 FE listing names AT&T, but does not specify whether the handset is unlocked. Carrier compatibility is a purchase requirement, not a minor extra: check supported network bands, SIM configuration, and lock status with the seller and your carrier. This is especially important for imported or refurbished devices, where a model name alone may not identify the exact regional variant.
Treat protection claims carefully
The OnePlus listing presents IP66, IP68, IP69, and IP19K ratings, while the S23 FE is described more generally as water resistant. The S21 Ultra description does not provide a protection rating. I would check manufacturer documentation for the exact model and region before relying on any rating. Water resistance can also change with wear or repairs, which is particularly relevant for a renewed device. Do not treat these specifications as permission to expose a phone to water beyond the manufacturer’s stated conditions.
Choose the tradeoff you can live with
For a buyer who wants the broadest listed hardware, the OnePlus 15 leads. The S21 Ultra trades newer listed capacity for zoom and S Pen features, and the S23 FE trades raw scale for a smaller screen. Each is a coherent choice when its role matches your habits. Before buying, make a short checklist of must-haves—carrier access, comfortable size, camera reach, storage, and acceptable condition—and eliminate any listing that cannot satisfy those needs.
Frequently Asked Questions
Which phone is the best overall flagship Android choice in this comparison?
I rank the OnePlus 15 first because its listed 16GB RAM, 512GB storage, 7,300 mAh battery, 165Hz AMOLED display, and unlocked dual-SIM support form the most complete package here. The S21 Ultra has a more distinctive zoom and S Pen proposition, while the S23 FE has the smallest screen, but neither matches the OnePlus on listed capacity. I would still verify the OnePlus’s regional model and protection claims before ordering.
Which option is best for zoom photography?
The Galaxy S21 Ultra is the clear candidate based on the supplied listing, which names a 108MP main camera and up to 100x zoom. That figure indicates reach rather than guaranteed image quality at the maximum setting, so I would look for sample photos from the exact model and check the renewed phone’s camera condition. The OnePlus lists three 50MP rear cameras but no comparable zoom claim in the provided details.
Which phone should I choose if I want more storage?
The OnePlus 15 lists 512GB, compared with 128GB for each Samsung. That extra capacity can help if you keep large games, downloaded shows, or a substantial photo and video library on the phone. If you mostly stream and store files elsewhere, the Samsung capacity may be enough. I would check the exact storage configuration in the seller’s listing, since the product variant matters.
Are the renewed Samsung phones a good choice?
They can make sense for buyers who want Samsung hardware with specific strengths—the S21 Ultra’s zoom and S Pen features or the S23 FE’s smaller 6.4-inch display—but condition is a central part of the decision. The listings do not state battery health, and the S21 Ultra may have minor cosmetic imperfections. I would confirm the renewal grade, what accessories are included, carrier status, return window, and any warranty terms before choosing either one.
Is the Galaxy S23 FE compatible with any carrier?
The supplied listing associates this renewed S23 FE with AT&T and does not identify it as unlocked. I would not assume it will work with another carrier based on the model name alone. Ask the seller to confirm lock status and supported network bands, then compare those details with your carrier’s compatibility requirements. The S21 Ultra and OnePlus listings explicitly describe unlocked status, which makes their carrier details clearer on the information provided.
Conclusion
My overall recommendation is the OnePlus 15 for buyers who want the most generous listed hardware, storage, battery capacity, and carrier flexibility. Choose the Galaxy S21 Ultra if a large screen, S Pen support, and long-range zoom are the features that will shape your daily use—and if renewed condition is acceptable after checking battery and seller terms. Pick the Galaxy S23 FE if you prefer a smaller Samsung display and can verify AT&T compatibility. The right choice is the one whose defining strength matches your routine, with condition and network fit confirmed before purchase.
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