Numerous companies have done play testing, and despite the console players getting all the aim assistance, etc. available on the console, even mediocre PC players will still mop the floor with them. The difference in controller speed and precision really is just that dramatic.
I hate controllers, but the last two Call of Duty games on PCs have added the stupid aim assist for controller users, and it's actually competitive. Those people have gotten pretty good with their silly controllers now that there's pro leagues and whatnot. They still need the aim assist training wheels though. Some people say the assists are stronger on PC, but I wouldn't know.