hi, air purifier or diffuser? which one would you choose? heard a lot of good things about yleo though

Air purifier and diffusers have very different uses so it's actually up to what and why you need them for. Air purifier, as the name suggests, clean indoor air -- they remove dust as well as allergents like animal dander and pollen. They don't necessarily do anything for humidity in the air. I haven't used a diffuser before but from what I know, diffusers are commonly used to diffuse essential oils for aromatherapy (correct me if I'm wrong). I don't think they have the same cleansing effect as a purifier. I'm not too much of an essential oil person so I'd go with the air purifier. The diffuser, to me, adds more "stuff" into the air while the purifier seems to be have a cleaning effect.