Dyson - Purifier Big+Quiet Formaldehyde vs Winix - C909
Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | Dyson - Purifier Big+Quiet Formaldehyde | Winix - C909 |
|---|---|---|
| Coverage | 100 m² | 50 m² |
| CADR | 640 m³/h | 500 m³/h |
| Min noise | 24 dB | 27 dB |
Between the Purifier Big+Quiet Formaldehyde and C909, the Purifier Big+Quiet Formaldehyde comes out ahead in coverage / cadr, while the C909 wins on several specs. Overall, the Purifier Big+Quiet Formaldehyde scores 89.3 and the C909 scores 77.7 on our Mars Score.
Which should you buy?
The Purifier Big+Quiet Formaldehyde is the clear pick on raw spec strength, leading by 11.6 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 Purifier Big+Quiet Formaldehyde if you care most about coverage / cadr. The biggest gaps in its favor are coverage, cadr, min noise. The single most decisive one: Coverage — 100.00% more. 100 m² vs 50 m².
The C909 similarly does not carry a headline advantage on the popular specs — look at the full table for category-specific deltas.
Both ship with comparable true hepa h13+, activated carbon, so those specs do not separate the two — focus on the differences below.
Bottom line: the Purifier Big+Quiet Formaldehyde 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: Dyson - Purifier Big+Quiet Formaldehyde or Winix - C909?
Dyson - Purifier Big+Quiet Formaldehyde leads the current Mars Score by 11.6 points.The more useful decision is the trade-off behind that result: compare cadr, coverage, min noise against the way you will actually use the product.
Choose Dyson - Purifier Big+Quiet Formaldehyde if…
Dyson - Purifier Big+Quiet Formaldehyde has the measurable edge on coverage m2, cadr m3h, noise db min.
Choose Winix - C909 if…
Winix - C909 does not lead a decisive measured field here, so choose it for price, ecosystem, design, or availability when those matter more to you.
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 Dyson - Purifier Big+Quiet Formaldehyde wins
- ▲Coverage — 100.00% more. 100 m² vs 50 m².
- ▲CADR — 28.00% more. 640 m³/h vs 500 m³/h.
- ▲Min noise — 3.00 dB less. 24 vs 27.
Why Winix - C909 wins
- No decisive advantages.
Spec comparison
Performance
| Spec | Dyson - Purifier Big+Quiet Formaldehyde | Winix - C909 |
|---|---|---|
| CADR | 640 m³/hlead | 500 m³/h |
| Coverage | 100 m²lead | 50 m² |
| True HEPA H13+ | true | true |
| Activated carbon | true | true |
Smart & Noise
| Spec | Dyson - Purifier Big+Quiet Formaldehyde | Winix - C909 |
|---|---|---|
| Min noise | 24 dBlead | 27 dB |
| Air quality sensor | true | true |
| Smart app | true | true |