I was really hanging out for Debian - but I must admit, I always liked sailfish for a phone os. It was built on mer, and as such is a fully functional Linux (unlike android).
It was also built for a phone, so I would guess phone features would work. Another plus is that it can run (some) android apps, so you can have the best of both worlds -
install your banks android app, and still have a secure full Linux to play with. You can install the build chain (gcc...) and compile/run apps in the terminal. I'll probably end
up trying them all, but as I have a 4G version, and it will be my daily driver, I am actually leaning towards sailfish. Bring back the days of the N900
Another issue is that debain/Ubuntu is great when plugged into a monitor, but I think it might be hard to read (small) whilst the phone based OSs already have this in hand.
PS. I develop all day in debian, hence my initial preference.