I have four installed on Android: Sync, Jerboa, Connect and Voyager. Five if you count Firefox which is the only one that does all the admin tasks I need. I switch between them because as admin I find myself testing the user experience frequently.
I have Memmy on iOS, but really only use iOS for testing purposes. I don't browse with it.
I default to Sync for most browsing and commenting because the Dev is very active and it's the only client I know of with any mod tools at all. It is the most polished of the clients at the moment.