I think that the idea of the bar having to travel farther is crap, with an exception I'll mention. If proportions stay the same, then the taller person given a proportional amount of muscle would bench proportionally more. In fact, a taller person with a high sticking point would actually have more time to accelerate the bar at the bottom.
NOW, most differences in height occur in the arms and legs. Ed Coan for example is 5-6 but he's said that sitting down he's as tall as a 6 footer also sitting down. The main differences in peoples height is determined by when the long bones of the legs stop growing-and the arms tend to follow. Since arm bones grow at the distal (far away) end, the muscular attachments (applied torque) are locked in rather early while the resistance torque may continue to rise as one grows.
Also, I am 5-8 with rather short arms, yet for a maximal bench, I have my index fingers on the power rings which is the widest legal grip. It seems about perfect for me. If I were 6-4, I'd certainly want to grip the bar another hands width out.