Well, as far as adjusting speeds for all races, what you suggest might be more realistic, but there are quite a few non-realistic things we ignore in the game for balance. I think this should be one of them.
I call for equality (in movement speed) amongst all playable races! Come on people, smile on your brother. Everybody get together, try to love one another right now :P
I call for equality (in movement speed) amongst all playable races! Come on people, smile on your brother. Everybody get together, try to love one another right now :P