Pacquiao with his fast feet and flurries of punches would probably prevent Williams from getting set in the early rounds, but Ike would eventually find a way through Pacquiao's defenses after which the sharp, accurate combinations would start pouring on. Think of the Marquez fights (not the upcoming fight with an ancient JMM) except with the power Williams possessed. Very difficult to get out of the way out Ike Williams once he had you read. Pacquiao has shown himself rather durable in recent times so he might hang in there until the final bell but Williams's clean, effective punching would win him the decision. There would be less controversy than the Marquez fights.
It would be close early on, but Ike's jab and accurate punching will ultimately be Manny's undoing. I like Williams by UD or late TKO, as Pac ultimately becomes too hurt.
I think Manny probably wins this with his footwork/movement, getting off first, although Ike may time him with some big shots
