I got fm07 for xbox because my pc is pretty ancient, and it would take a minor miracle for my pc to support just 10 leagues with a normal database. I had the demo to compare with, and xbox is much faster, so With xbox i dont have to worry about processing time, and i can play with 10 leagues (altho only with a small database). I read in one other review, sorry i cant quote directly, but they said that the xbox version processes 3 to 4 times faster than a high end pc.
Overall, i think the pc version is obviously much cleaner, and overall looks much better. Im not a fan of the gross looking grey tabs, and the pitch and players are much to small on the xbox. Im still a fan of the mouse and keyboard, but ive had no problem adjusting to the controller, which seems to be a problem blown out of proportion.
Anyways, it all depends on what your looking for. Speed, or aesthetics. Xbox in my opinion is what you want to run a decent amount of leagues and at a good pace. PC version is what you want if you like the clean look, and large databases, and the free roam of the mouse.. I do warn you not to base your judgement on mouse v. controller, as the controller is very easy and intuitive to use once you get used to. and one other thing to note, do you like to laze on your couch, or be sittin up in a computer chair? food for thought.
If you do have a very highend pc, than i suggest the pc version, as im even a bit more biased towards pc, and sometimes find myself wishing i could have my pretty version of fm07 back...BUT, then again, ive never played through a campaign so fast before.
Hope this helps.