Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | WHOOP - 5.0 | Xiaomi - Smart Band 9 |
|---|---|---|
| Battery life | 14 days | 21 days |
| Sport modes | 120 | 150 |
| Water resistance | 10 ATM | 5 ATM |
Between the 5.0 and Smart Band 9, the 5.0 comes out ahead in water resistance, while the Smart Band 9 wins on battery life / sport modes. Overall, the 5.0 scores 66.6 and the Smart Band 9 scores 75.8 on our Mars Score.
Which should you buy?
The Smart Band 9 is the clear pick on raw spec strength, leading by 9.2 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 5.0 if you care most about water resistance. The biggest gaps in its favor are water resistance. The single most decisive one: Water resistance — 5.00 ATM more. 10 vs 5.
Pick the Smart Band 9 if you care most about battery life / sport modes. Its strongest claims are battery life, sport modes. The single most decisive one: Battery life — 50.00% more. 21 days vs 14 days.
Both ship with comparable gps, spo2, so those specs do not separate the two — focus on the differences below.
Bottom line: the Smart Band 9 is the safer default. The other model is the right choice only when its specific advantages line up with your priorities.
Which should you buy: WHOOP - 5.0 or Xiaomi - Smart Band 9?
Xiaomi - Smart Band 9 leads the current Mars Score by 9.2 points.The more useful decision is the trade-off behind that result: compare battery life against the way you will actually use the product.
Choose WHOOP - 5.0 if…
WHOOP - 5.0 has the measurable edge on water resistance atm.
Choose Xiaomi - Smart Band 9 if…
Xiaomi - Smart Band 9 has the measurable edge on battery days, sport modes.
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 WHOOP - 5.0 wins
- ▲Water resistance — 5.00 ATM more. 10 vs 5.
Why Xiaomi - Smart Band 9 wins
- ▲Battery life — 50.00% more. 21 days vs 14 days.
- ▲Sport modes — 30.00 more. 150 vs 120.
Spec comparison
Fitness
| Spec | WHOOP - 5.0 | Xiaomi - Smart Band 9 |
|---|---|---|
| GPS | false | false |
| Heart rate | true | true |
| SpO2 | true | true |
| Sleep tracking | true | true |
| Sport modes | 120 | 150lead |
Battery
| Spec | WHOOP - 5.0 | Xiaomi - Smart Band 9 |
|---|---|---|
| Battery lifeⓘ | 14 days | 21 dayslead |
| Water resistanceⓘ | 10 ATMlead | 5 ATM |
Design
| Spec | WHOOP - 5.0 | Xiaomi - Smart Band 9 |
|---|---|---|
| Display size | 0 " | 1.62 "lead |
| Weight | 21 g | 16 glead |