In order to accurately answer this question, you need to consider that in this whole thing between PC gamers and Xbox360 gamers playing together, there's a FPS coming out which I can't remember the name of (Let's call it UT clone for argument's sake), and when a member of PC Zone pointed out to the developers that because the PC allows for more precision thanks to the keyboard, the PC gamers would have a bigger advantage. Not so, apparently, because they're loosening out the mouse movement.

That tells you all you need to know.

Mouse+Keyboard FTW.