Nothing Phone 3 vs Xiaomi 15 Ultra: Is the Xiaomi 15 Ultra Worth £720 More?
Nothing Phone 3 or Xiaomi 15 Ultra? We compare price, measured performance and real-world trade-offs to work out which is the better buy.
Priya Raghunathan
The short answer
Nothing Phone 3 7h 20m, Xiaomi 15 Ultra 7h 05m — the same test, run the same way. Where they part company is who they suit: the Nothing Phone 3 is the one to get if you are buyers who want flagship battery and software without flagship pricing, the Xiaomi 15 Ultra if you are photographers who want the closest thing to a compact camera in a phone.
Price difference: The Nothing Phone 3 undercuts the Xiaomi 15 Ultra by £720. That gap only matters if the extras below are ones you will actually use.
Specifications side by side
| Specification | Nothing Phone 3 | Xiaomi 15 Ultra |
|---|---|---|
| Price | £579 | £1299 |
| Our score | 4 / 5 | 4 / 5 |
| Display | 6.7in AMOLED, 120Hz | 6.73in LTPO AMOLED, 120Hz |
| Chip | Snapdragon 7+ Gen 3 | Snapdragon 8 Elite |
| RAM | 12GB | 16GB |
| Battery | 5000mAh | 5410mAh |
| Charging | 45W wired | 90W wired |
| Weight | 198g | 226g |
| Screen-on time | 7h 20m | 7h 05m |
How we tested
Every figure quoted above comes from the same protocol, run on every unit in this category. This one spent fourteen days as the reviewer’s only phone, SIM included. Screen at a metered 200 nits, adaptive refresh left on, the same twelve apps installed on every handset, and a fixed 5G network in the same building.
| What we measure | How |
|---|---|
| Screen-on time | A scripted day — four hours of mixed browsing, an hour of video, thirty minutes of camera, the rest idle — repeated three times and averaged. |
| Sustained performance | Twenty minutes of continuous load, reporting the figure at the end rather than the peak in the first ninety seconds. |
| Charging | From 2% to 100% with the fastest charger the manufacturer sells, at 22°C ambient, timed to the minute. |
| Camera | The same eighteen scenes on every phone — backlit portrait, indoor low light, moving subject — shot in the default mode with no editing. |
| Thermals | Surface temperature at the hottest point after the sustained run, measured with a contact probe. |
We deliberately do not report synthetic benchmark totals quoted in isolation, and any figure supplied by the manufacturer.
The honest caveat: Battery results are specific to our routine. A heavy camera user will see materially less screen-on time than these numbers suggest.
Where the Nothing Phone 3 wins
- Excellent battery life
- Clean software with almost no preinstalled clutter
- A design that still stands out
It also has the edge on the intangibles: the Glyph lights have become genuinely useful as a delivery and timer readout.
Where the Xiaomi 15 Ultra wins
- A one-inch main sensor with genuinely optical depth falloff
- An optional grip with a physical shutter
- Very fast charging
And in day-to-day use, night mode is rarely needed at all thanks to the sensor size.
The trade-offs
Neither is flawless. The Nothing Phone 3 has one clear weak point — weak low-light photography — and the Xiaomi 15 Ultra has its own: heavy. Weigh those against how you actually work rather than against the spec sheet.
The value case
Both scored 4 out of 5, and the Nothing Phone 3 costs £720 less. Unless a one-inch main sensor with genuinely optical depth falloff is specifically what you need, the cheaper one is the better buy and we would not agonise over it.
If neither quite fits
Look at the Pixel 9a at £499 — it scored 5 out of 5 and suits almost everyone — the sensible default recommendation. If the budget will not stretch, the Galaxy A56 at £399 is the cheapest option in this category we would still put our name to.
Living with each of them
On paper the gap looks like a specification difference; in use it is a habits difference. With the Nothing Phone 3 the thing you adjust to is weak low-light photography, and you do adjust — within a week it stops registering. Its display (6.7in AMOLED, 120Hz) is the part you stop thinking about. The Xiaomi 15 Ultra asks for a different accommodation: heavy, against a display of 6.73in LTPO AMOLED, 120Hz that holds up better than the number suggests. Neither compromise is severe. They are simply different, and which one you would rather not think about is a more useful question than which is objectively smaller.
Which one ages better
Both launched in 2025, so neither starts with a support-window advantage. The other half of ageing is the weak point you already know about: weak low-light photography on one side, heavy on the other. Weaknesses of that kind do not improve with firmware, so assume you are buying them for the life of the device and price the decision accordingly.
Our recommendation
For most people we would take the Nothing Phone 3, which scored 4 out of 5 in our testing against 4 for the other. That said, a score is a summary, not a substitute for knowing what you need.
Buy the Nothing Phone 3 for excellent battery life. Buy the Xiaomi 15 Ultra for a one-inch main sensor with genuinely optical depth falloff.
Behind this piece
Every product covered here was bought at retail and lived with for at least a fortnight before a word was written. Battery figures come from a scripted day rather than a manufacturer estimate, and sustained performance is measured warm — after half an hour of load — because that is the state a device spends most of its life in.
Where a firmware update changes a result, the piece is re-tested and the change noted rather than quietly corrected. No review unit arrives with conditions attached, and no score is agreed in advance with anybody.
Where to go next
If you are weighing this against the rest of the smartphones we have covered, the category archive lists every review in date order. The closest comparisons we have published are Nothing Phone 3: Battery Draining Faster Than It Should and Nothing Phone 3: Bluetooth Keeps Disconnecting.
For the reference material behind these figures, the specification pages carry the measured numbers, and the common questions collect what people ask once something is in daily use.
