Between the T-Rex 3 and OnePlus Watch 3, the T-Rex 3 comes out ahead in battery life and weight, while the OnePlus Watch 3 wins on peak brightness and ecg. Overall, the T-Rex 3 scores 79.7 and the OnePlus Watch 3 scores 53.9 on our Mars Score.
Which should you buy?
The T-Rex 3 is the clear pick on raw spec strength, leading by 25.8 points on the Mars Score. The margin is wide enough that the underdog only makes sense if its individual strengths line up with what you specifically need.
Pick the T-Rex 3 if your top frustration with your current device is running out of charge before the day ends — endurance is the lead spec here. The biggest gaps in its favor are battery life, weight, water resistance.
Pick the OnePlus Watch 3 if the display is what you stare at all day — refresh rate, brightness, or sharpness is where the difference will be most visible. Its strongest claims are peak brightness, ecg.
Both ship with comparable display size, cellular, spo2, so those specs don't separate the two — focus on the differences below.
Bottom line: the T-Rex 3 is the safer default. The other model is the right choice only when its specific advantages line up with your priorities.
Why Amazfit - T-Rex 3 wins
- ▲Battery life — 460.00% more. 672 h vs 120 h.
- ▲Weight — 13.00 g less. 68 vs 81.
- ▲Water resistance — 5.00 ATM more. 10 vs 5.
Why OnePlus Watch 3 wins
- ▲Peak brightness — 10.00% more. 2200 nits vs 2000 nits.
- ▲Has ECG.
Spec comparison
Design
| Spec | Amazfit - T-Rex 3 | OnePlus Watch 3 |
|---|---|---|
| Case size | 48.5 mmlead | 46.5 mm |
| Weight | 68 glead | 81 g |
| Case material | polymer | stainless steel |
| Water resistanceⓘ | 10 ATMlead | 5 ATM |
Display
| Spec | Amazfit - T-Rex 3 | OnePlus Watch 3 |
|---|---|---|
| Display size | 1.5 " | 1.5 " |
| Always-on display | true | true |
| Peak brightnessⓘ | 2000 nits | 2200 nitslead |
Health & Fitness
| Spec | Amazfit - T-Rex 3 | OnePlus Watch 3 |
|---|---|---|
| ECG | false | truelead |
| SpO2 | true | true |
| Temperature sensor | true | true |
| Sleep tracking | true | true |
| Blood pressure | false | false |
Battery & Connectivity
| Spec | Amazfit - T-Rex 3 | OnePlus Watch 3 |
|---|---|---|
| Battery life | 672 hlead | 120 h |
| GPS | true | true |
| Cellular | false | false |
| NFC | false | truelead |
| OS | Zepp OSlead | WearOS |
Frequently asked
Which has longer battery life, T-Rex 3 or OnePlus Watch 3?+
T-Rex 3 lasts 672h vs 120h.
Do T-Rex 3 or OnePlus Watch 3 support ECG?+
OnePlus Watch 3 supports ECG; T-Rex 3 does not.
Which has cellular, T-Rex 3 or OnePlus Watch 3?+
Neither offers cellular.
Spec-level deep dives
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