Tiger's shortgame was way ahead of Rory's at his best and Rory's obviously struggled on the greens in the last couple of years but I think the biggest difference is the rest of the field. Tiger wasn't just good on his own, he was playing against a field that wasn't as good as it has been in the last 6 or 7 years. If Rory and Tiger were the same age now, I think they'd be roughly equivalent in success.
First and foremost the players play the course.
the countless rounds under par, massive winning margins. Woods at his best for me is still better than Rory at his best. The biggest difference was that woods was at his best for years. Nit months at a turn.
Their top game may be similar. But woods had his top game far more often.