So are you saying that using a mouse against a joystick opponent is an unfair advantage?

Isn't ease of use a good thing?

Another advantage PCs have is more keys than you could ever effectively use. However, it takes an expert to use a large number of those keys well.

A player will be good with whatever they play repeatedly on. Maybe the real question is not which is easier, but which has a higher ceiling of skill, that is, given two people of the same skill and physical ability, and given the same amount of time and the same game to train on, will the mouse or gamepad player become better? This may also have to be restricted by genre as well. i.e. mouse may have a higher skill ceiling on FPS but lower than console on sports or beat-em-ups.