Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | Garmin - Fenix 8 (47mm) | Xiaomi - Watch S4 |
|---|---|---|
| Peak brightness | 1000 nits | 2200 nits |
| Weight | 73 g | 44 g |
| Battery life | 384 h | 360 h |
| Water resistance | 10 ATM | 5 ATM |
| Display size | 1.4 " | 1.43 " |
| Cellular | false | true |
Between the Fenix 8 (47mm) and Watch S4, the Fenix 8 (47mm) comes out ahead in battery life / water resistance, while the Watch S4 wins on peak brightness / weight. Overall, the Fenix 8 (47mm) scores 71.9 and the Watch S4 scores 76.3 on our Mars Score.
Which should you buy?
The Watch S4 edges ahead on the Mars Score (71.9 vs 76.3), but the 4.4-point gap is small enough that the right pick comes down to which spec advantages matter to you.
Pick the Fenix 8 (47mm) 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, water resistance. The single most decisive one: Battery life — 6.67% more. 384 h vs 360 h.
Pick the Watch S4 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, weight, display size, among others. The single most decisive one: Peak brightness — 120.00% more. 2200 nits vs 1000 nits.
Both ship with comparable ecg, spo2, 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: Garmin - Fenix 8 (47mm) or Xiaomi - Watch S4?
Xiaomi - Watch S4 leads the current Mars Score by 4.4 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 Garmin - Fenix 8 (47mm) if…
Garmin - Fenix 8 (47mm) has the measurable edge on battery life h, water resistance atm.
Choose Xiaomi - Watch S4 if…
Xiaomi - Watch S4 has the measurable edge on peak brightness nits, weight g, display size in.
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 Garmin - Fenix 8 (47mm) wins
- ▲Battery life — 6.67% more. 384 h vs 360 h.
- ▲Water resistance — 5.00 ATM more. 10 vs 5.
Why Xiaomi - Watch S4 wins
- ▲Peak brightness — 120.00% more. 2200 nits vs 1000 nits.
- ▲Weight — 29.00 g less. 44 vs 73.
- ▲Display size — 2.14% more. 1.43 " vs 1.4 ".
- ▲Has Cellular.
Spec comparison
Design
| Spec | Garmin - Fenix 8 (47mm) | Xiaomi - Watch S4 |
|---|---|---|
| Case size | 47 mm | 47 mm |
| Weight | 73 g | 44 glead |
| Case material | fiber-reinforced polymer | stainless steel |
| Water resistanceⓘ | 10 ATMlead | 5 ATM |
Display
| Spec | Garmin - Fenix 8 (47mm) | Xiaomi - Watch S4 |
|---|---|---|
| Display size | 1.4 " | 1.43 "lead |
| Always-on display | true | true |
| Peak brightnessⓘ | 1000 nits | 2200 nitslead |
Health & Fitness
| Spec | Garmin - Fenix 8 (47mm) | Xiaomi - Watch S4 |
|---|---|---|
| ECG | true | true |
| SpO2 | true | true |
| Temperature sensor | true | true |
| Sleep tracking | true | true |
| Blood pressure | false | false |
Battery & Connectivity
| Spec | Garmin - Fenix 8 (47mm) | Xiaomi - Watch S4 |
|---|---|---|
| Battery lifeⓘ | 384 hlead | 360 h |
| GPS | true | true |
| Cellular | false | truelead |
| NFC | true | true |
| OS | Garmin OSlead | HyperOS |
Frequently asked
Which has longer battery life, Fenix 8 (47mm) or Watch S4?+
Fenix 8 (47mm) lasts 384 hours vs 360 hours.
Do Fenix 8 (47mm) or Watch S4 support ECG?+
Both support ECG.
Which has cellular, Fenix 8 (47mm) or Watch S4?+
Watch S4 offers a cellular variant; Fenix 8 (47mm) is Wi-Fi only.