25i

Considering the current Coway price tags, I prefer Alen. I have the Coway Airmega 400S and 300S and then recently got the Alen 25i for my small office. Alen hands down has the most pleasant sound. Plus they come with a lifetime warranty if you buy their filters which are reasonably priced.

Here In US we don't have Phillips so much, so I've never had one, although they do some popular/common in posting in here and are probably OK. I have multiple Levoits though and love them. As for being quiet in sleep mode you might want to look at th Levoit unit sprout, that is more for a nightstand