The Xiaomi Mi Air 3C (PM CADR 320m3/h) is less powerful than the 3H (PM CADR 380m3/h).
The area performance of the 3H is 126m2/h compared to the 106m2/h of the 3C.
On the other hand, the 3C is a little quieter and the replacement of the filter has been improved.
Xiaomi recommends the 3C for bedrooms and offices.
The 3H for bedrooms and children's rooms.
For larger rooms (e.g. living room), the Mi Air Purifier Pro (H) is intended.