Pac takes him. Terrific jaw, speed, angles, aggression, and quite a bit of pop himself. Tsyzu struggled against all these attributes at one point or another, and was broken when Hatton put some of them together when he was aging. Tsyzu is an ATG, but this is a toxic style match up for him.
I picked Tszyu pts in a dream fight for Ray Wheatley's World of Boxing last year. Tszyu would land enough straight rights to keep Manny honest. Tszyu loved lefties. Johnny Lewis' conditioning gets him over the line.
Pac would only fight Tszyu if it is past his prime Kostya. Prime any half decent fighter who isnt slow as molases beat the overrated Pac.
He did pretty well against the likes of Mitchell and Judah lasering in that righthand. I would say Pac would be a bit easier to find than those guys.
Tszyu and Pac are both thinking fighters though. I think Tszyu would've had a workable game plan to take on Pac. Not putting down Pac at all, he is a machine but damn, this would've been a great fight.
Tyszu's right is probably as straight and accurate as JMM's and he uses the angles very well against Southpaws. Pacquaio is faster and may work at a pace Tyszu won't like although the counter punching may slow him down, still he can be timed and he will come in straight lines making him easier to time than Mtchell for instance. Tyszu has the body punching and strength over Pac too. Could go either way