Amazfit - T-Rex 3 vs Apple - Watch Ultra 3 vs Withings - ScanWatch 2
Across Amazfit - T-Rex 3, Apple - Watch Ultra 3, and Withings - ScanWatch 2, the Amazfit - T-Rex 3 takes the highest Mars Score (79.7), followed by Withings - ScanWatch 2 (72.6) and Apple - Watch Ultra 3 (65.3). See the full readout below.
Pick the Amazfit - T-Rex 3 if you want the highest-scoring choice on raw spec strength. The 7.1-point gap to the runner-up is wide — the chart-topper is the safer default.
Pick the Withings - ScanWatch 2 when you want the spec advantages it carries over the leader (look at the per-product breakdown below).
Pick the Apple - Watch Ultra 3 only if its specific strengths align with what you need — it sits well behind the other two on the Mars Score.
Spec comparison
Design
| Spec | T-Rex 3 | Watch Ultra 3 | ScanWatch 2 |
|---|---|---|---|
| Case size | 48.5 mm | 49 mm | 42 mm |
| Weight | 68 g | 62 g | 59 g |
| Case material | polymer | titanium | stainless steel |
| Water resistanceⓘ | 10 ATM | 10 ATM | 5 ATM |
Display
| Spec | T-Rex 3 | Watch Ultra 3 | ScanWatch 2 |
|---|---|---|---|
| Display size | 1.5 " | 2.04 " | 0.63 " |
| Always-on display | true | true | false |
| Peak brightnessⓘ | 2000 nits | 3000 nits | 0 nits |
Health & Fitness
| Spec | T-Rex 3 | Watch Ultra 3 | ScanWatch 2 |
|---|---|---|---|
| ECG | false | true | true |
| SpO2 | true | true | true |
| Temperature sensor | true | true | true |
| Sleep tracking | true | true | true |
| Blood pressure | false | false | false |
Battery & Connectivity
| Spec | T-Rex 3 | Watch Ultra 3 | ScanWatch 2 |
|---|---|---|---|
| Battery life | 672 h | 72 h | 720 h |
| GPS | true | true | false |
| Cellular | false | true | false |
| NFC | false | true | false |
| OS | Zepp OS | watchOS | Withings OS |
Pairwise deep dives
Frequently asked
Which scores highest overall: Amazfit - T-Rex 3, Apple - Watch Ultra 3, or Withings - ScanWatch 2?+
Amazfit - T-Rex 3 scores highest at 79.7, followed by Withings - ScanWatch 2 (72.6) and Apple - Watch Ultra 3 (65.3).
Which is the newest of Amazfit - T-Rex 3, Apple - Watch Ultra 3, and Withings - ScanWatch 2?+
Apple - Watch Ultra 3 is the most recent, released 2025-09-19.
Which has longer battery life, Amazfit - T-Rex 3 or Withings - ScanWatch 2?+
Withings - ScanWatch 2 lasts 720 hours vs 672 hours.
Do Amazfit - T-Rex 3 or Withings - ScanWatch 2 support ECG?+
Withings - ScanWatch 2 supports ECG; Amazfit - T-Rex 3 does not.
Which has cellular, Amazfit - T-Rex 3 or Withings - ScanWatch 2?+
Neither offers cellular.
One spec at a time
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