Well the difference is being 'hardcoded' for WASD or say a 360 controller. Me personally any game I've played on both 360 and PC ends in a horrible death for me on the console. I am very gimped when trying to play FPS games on a console, due to unresponsive controls.
But personally there have been so many specialized controllers for games over the years, it's sorta amazing that a mouse and keyboard hasn't seen more on the console side of things.