PS3 controller for me. Everything is in close reach, and its just what I'm most used to.
I recently got Steam, and a few games for my PC now, so< I'm kinda getting the hang of mouse and keyboard, but, I'm nowhere near as fluent with that as I am with any controller.
I think my biggest beef with mouse and keyboard is, when it comes to FPS' the mouse is far clunkier than dual analog sticks. Its difficult to make quick 180 degree spins without having your sensitivity ridiculously high. You have to move the mouse as far as you can, lift it and move back to the other side, and then slide all the way over again, rinse and repeat. It just feels choppy.
Also, as far as the keyboard goes, the keys never feel as natural as buttons. Just, the placement of the keys makes it awkward for quick and responsive button presses. Even with everything hotkeyed to where I want it, something always feels out of place.
This is probably all because I started my gaming life with an N64 controller, and then progressed to Ps2 and then Ps3, so, I'll probably never be at the level I am with controllers with a mouse and keyboard scheme.