As far as I am aware, the general concensus is that the shorter the player the faster he trains in guard skills.
There has been some research done on it and it seems to point to this conclusion.
While it might be different in reality, in the game a 5'11" will train OD faster than a 6'3" guy, and a 7'4" guy will train faster in Rebounding than a 6'11" guy.