Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | Withings - ScanWatch 2 | Xiaomi - Watch S4 |
|---|---|---|
| Display size | 0.63 " | 1.43 " |
| Battery life | 720 h | 360 h |
| Weight | 59 g | 44 g |
| Cellular | false | true |
| Peak brightness | 0 nits | 2200 nits |
Between the ScanWatch 2 and Watch S4, the ScanWatch 2 comes out ahead in battery life, while the Watch S4 wins on display size / weight. Overall, the ScanWatch 2 scores 78.3 and the Watch S4 scores 76.3 on our Mars Score.
Which should you buy?
These two are nearly even on the Mars Score (78.3 vs 76.3). The decision is not about overall quality — both clear the bar — it is about which specific trade-offs fit your use.
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. The biggest gaps in its favor are battery life. The single most decisive one: Battery life — 100.00% more. 720 h vs 360 h.
Pick the Watch S4 if you carry the device everywhere and weight or thickness has been the deciding factor before. Its strongest claims are display size, weight, cellular, among others. The single most decisive one: Display size — 126.98% more. 1.43 " vs 0.63 ".
Both ship with comparable ecg, spo2, water resistance, so those specs do not separate the two — focus on the differences below.
Bottom line: there is no wrong answer here — match the spec advantages to how you actually use the product. The Mars Score parity says both are well-rounded; the differences are about trade-offs, not quality.
Which should you buy: Withings - ScanWatch 2 or Xiaomi - Watch S4?
Withings - ScanWatch 2 leads the current Mars Score by 2.0 points.The more useful decision is the trade-off behind that result: compare display size, battery life against the way you will actually use the product.
Choose Withings - ScanWatch 2 if…
Withings - ScanWatch 2 has the measurable edge on battery life h.
Choose Xiaomi - Watch S4 if…
Xiaomi - Watch S4 has the measurable edge on display size in, weight g, has cellular.
This is a structured comparison of the published catalog values. It is not a claim of identical real-world performance across every workload; use the linked spec drill-downs and methodology page to inspect the inputs.
Why Withings - ScanWatch 2 wins
- ▲Battery life — 100.00% more. 720 h vs 360 h.
Why Xiaomi - Watch S4 wins
- ▲Display size — 126.98% more. 1.43 " vs 0.63 ".
- ▲Weight — 15.00 g less. 44 vs 59.
- ▲Has Cellular.
- ▲Peak brightness: 2200 nits vs 0 nits.
Spec comparison
Design
| Spec | Withings - ScanWatch 2 | Xiaomi - Watch S4 |
|---|---|---|
| Case size | 42 mm | 47 mmlead |
| Weight | 59 g | 44 glead |
| Case material | stainless steel | stainless steel |
| Water resistanceⓘ | 5 ATM | 5 ATM |
Display
| Spec | Withings - ScanWatch 2 | Xiaomi - Watch S4 |
|---|---|---|
| Display size | 0.63 " | 1.43 "lead |
| Always-on display | false | truelead |
| Peak brightnessⓘ | 0 nits | 2200 nitslead |
Health & Fitness
| Spec | Withings - ScanWatch 2 | Xiaomi - Watch S4 |
|---|---|---|
| ECG | true | true |
| SpO2 | true | true |
| Temperature sensor | true | true |
| Sleep tracking | true | true |
| Blood pressure | false | false |
Battery & Connectivity
| Spec | Withings - ScanWatch 2 | Xiaomi - Watch S4 |
|---|---|---|
| Battery lifeⓘ | 720 hlead | 360 h |
| GPS | false | truelead |
| Cellular | false | truelead |
| NFC | false | truelead |
| OS | Withings OSlead | HyperOS |
Frequently asked
Which has longer battery life, ScanWatch 2 or Watch S4?+
ScanWatch 2 lasts 720 hours vs 360 hours.
Do ScanWatch 2 or Watch S4 support ECG?+
Both support ECG.
Which has cellular, ScanWatch 2 or Watch S4?+
Watch S4 offers a cellular variant; ScanWatch 2 is Wi-Fi only.