I think Pac wins a fun fight. Not that Cotto fights similar to Taylor (nor was he as good as peak Taylor), but I see a case where Pacquiao has success in both the exchanges as well as him using movement with his super fast foot speed, as he did against Cotto. Taylor would be a tougher fight, but I think Pacquiao stops Taylor late, or drops him en route to a clear decision.
I think Taylor stops him late. PAC will win more rounds and force Taylor to follow but he'd catch up to him late. Once pac starts trying to take breaks on the ropes with his gloves up he gets roasted.
Pick em fight. Battle of speed. I think Manny was more dynamic, though. He'd pull out a decision in a fun fight. Now Whitaker, Pryor, and Benitez beat the hell outta Manny at 140.
Even against the boxing equivalent of the blob, Margarito, Pac stopped on the ropes and corners and let him unload. Morales did it, Marquez did it, Bradley did it... Hell, Horn did it. When he's forced near the ropes and he's not sure whether to attack or move sometimes he just goes into a peekaboo and it wouldn't work well against a guy with super fast hands.