I see through my own eyes, so why would I want to be reminded that Skyrim is just a game by having an over the shoulder view?
I can see my whole body with my eyes and whats happening to the side of me with my eyes in RL but I can only see my hands in 1st person in game.
I go with 3rd almost always. I just can't get used to seeing to hands out in front of me like that and when I am fighting with sword or something like that I am never able to correctly judge the distance for some reason, which is really the primary reason for me always being in third. Everything just works better for me.