After being a hardcore CS:source clan player, to a console player putting in lots of hours (I try to play for fun but still hate losing).
I have to say it's down to choice.
I hated having to constantly update my PC, buy new bits and upgrade others. It just got on my tits! Console gaming makes it much easier.
But the mouse v controller argument, mouse wins everytime.
The precision a mouse can move at compared to a controller is unreal, hence why console games have that gay assed sticky aim, does my nut in!
You don't need that on a PC, as if you flick your mouse never mind doing a 360, you've probably just done a 720. It's so easy to home in on someone with a mouse as you are completely in control of it's movement the whole time. There's no flick back off the sticks like a controller.
Easiest way to judge is watch a MLG match or the like, same game, watch a console match, then watch a PC match. You will see for yourself.