I agree with this. Pac is more dynamic in the way he delivers his power, but I think Cotto straight up hits with more force.
I'd say that Pac hits sharper, quicker than Cotto, meaning that the effect of the punch is greater, but that Cotto hits heavier. Sounds silly but I was watching the making of Rocky Balboa, and Stallone was talking about the noises he used for editing the boxing scences. Mason Dixson's punches were sharper and faster, so the noise had more of a snap to it, where as the slower Balboa would land heavier, with more mass, so the noise used was more of a dull fud, I think that describes the two punchers here.
imo, cotto hits harder than pacquiao. pacquiao does hit you fast and from unexpected directions so it does add to the shock but punch per punch, i'd say cotto hits harder.