What is the major difference between these two models? Specially brakes calipers?
I find the 7800 brake/shift lever hoods to be much more comfortable than the 7700. The brake levers are also easier to reach from the drops. The cranks are also easier to take off to clean around BB area, as well as being lighter and stiffer (not that I was flexing the old style). Shifting is a little better, a shorter throw maybe?