Skills or physical abilities?

Floyd is already visibly aging as a boxer. Pacquiao isn't yet.

Mayweather relies a lot on his speed and reflexes. So time will hurt him also.

Floyd's more skilled than Manny but alot of the things he does in the ring are highly dependent on athletic ability/sharp reflexes and that'll eventually decline with age as well, assuming he's waiting on Manny to get old like Max Kellerman suggested(I don't know/care to speculate) that could backfire on him Hard to say but I think without Pac's quick footwork and handspeed, Floyd will easily outbox him for a 12 rd UD.