It totally buy a phone on the UI, surely the most important part of every phone? I agree the GS3 has a surprisingly decent camera, my brother has one and I am v impressed. To be fair to the N8, its an old phone now, the 808 is the new Daddy (if you ignore *ahem* Symbian).
I guess it depends if you put roms on or not, I always run custom roms so I can have any feel to the phone I want be it stock ICS, they even got a HTC rom on it now but with a custom launcher you lose the Touchwiz UI if you don't like it.