Between the T-Rex 3 and ScanWatch 2, the T-Rex 3 comes out ahead in display size and water resistance, while the ScanWatch 2 wins on weight and battery life. Overall, the T-Rex 3 scores 79.7 and the ScanWatch 2 scores 72.6 on our Mars Score.
Which should you buy?
The T-Rex 3 edges ahead on the Mars Score (79.7 vs 72.6), but the 7.1-point gap is small enough that the right pick comes down to which spec advantages matter to you.
Pick the T-Rex 3 if the display is what you stare at all day — refresh rate, brightness, or sharpness is where the difference will be most visible. The biggest gaps in its favor are display size, water resistance, peak brightness.
Pick the ScanWatch 2 if your top frustration with your current device is running out of charge before the day ends — endurance is the lead spec here. Its strongest claims are weight, battery life, ecg.
Both ship with comparable 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
- ▲Display size — 138.10% more. 1.5 " vs 0.63 ".
- ▲Water resistance — 5.00 ATM more. 10 vs 5.
- ▲Peak brightness: 2000 nits vs 0 nits.
Why Withings - ScanWatch 2 wins
- ▲Weight — 9.00 g less. 59 vs 68.
- ▲Battery life — 7.14% more. 720 h vs 672 h.
- ▲Has ECG.
Spec comparison
Design
| Spec | Amazfit - T-Rex 3 | Withings - ScanWatch 2 |
|---|---|---|
| Case size | 48.5 mmlead | 42 mm |
| Weight | 68 g | 59 glead |
| Case material | polymer | stainless steel |
| Water resistanceⓘ | 10 ATMlead | 5 ATM |
Display
| Spec | Amazfit - T-Rex 3 | Withings - ScanWatch 2 |
|---|---|---|
| Display size | 1.5 "lead | 0.63 " |
| Always-on display | truelead | false |
| Peak brightnessⓘ | 2000 nitslead | 0 nits |
Health & Fitness
| Spec | Amazfit - T-Rex 3 | Withings - ScanWatch 2 |
|---|---|---|
| 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 | Withings - ScanWatch 2 |
|---|---|---|
| Battery life | 672 h | 720 hlead |
| GPS | truelead | false |
| Cellular | false | false |
| NFC | false | false |
| OS | Zepp OSlead | Withings OS |
Frequently asked
Which has longer battery life, T-Rex 3 or ScanWatch 2?+
ScanWatch 2 lasts 720h vs 672h.
Do T-Rex 3 or ScanWatch 2 support ECG?+
ScanWatch 2 supports ECG; T-Rex 3 does not.
Which has cellular, T-Rex 3 or ScanWatch 2?+
Neither offers cellular.
Spec-level deep dives
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