Comfort is actually a part of it as well. The hoods on brifters have been more comfortable than the grips on the flat bar. (what little riding I have done on either..)
Gloves? New grips? It seems like there is a fair amount of pressure being exerted on my palms on the flat bar, where as in the hoods, it seems to be more on my wrist. (Or dissipated in some other fashion I do not understand.)