I have it on both formats and while I think the PC game is both better graphically and will have a fantastic modder's community, I tend to currently play it more on the 360. The reasoning, I have a big comfy lazyboy to sit in, a 55 inch TV to play it on and I like the xbox controller. That's not to say I don't play it on PC because I do (normally whenever its my wife's turn to venture into the realm of Skyrim)
I could move the PC into the lounge i suppose.... hmmmmm.... wonder what the wife would say to that... lol
Anyway, you can transfer your saves between both the 360 and PC formats... so I when I do play on the PC, i just import the 360 save and continue from there..... its all good