Not quite a benchmark, but try this:
Open a quicktime movie and click & hold your mouse on the tracker (in the trackbar

), then move the tracker around and see how the movie is displayed (really choppy, you see it loading the current frame every time you hold your mouse still for a second). Now imagine doing this on a Mac. It's just displaying like it's actaully playing the movie; instant updates, no jumpy stuff at all. backward and forward!
Ofcourse it's not quite what you've asked for, but it sure as hell shows you what Mac's can do best

.