I don't know about folio cases (I've always carried my phones in my pocket if they were small enough, or on my belt), but I've been using the iBlason holster case ($12.99 now at Amazon) for over 6 months, and the phone feels funny without it. It's TPU, so it takes up a lot of the shock if you drop the phone, it's not slippery, so it's difficult to drop the phone unless you're careless, and the case protrudes about 1/16" past the screen, so even if you do drop it face down, it's the case that takes the shock. It also has a nice little kickstand if you want to prop the phone up in landscape mode to watch TV or a movie.
The TPU part is black on all of them, but the colored part can be taken off, so it can probably be cleaned pretty vigorously.