Stature has always played a roll in the initial reaction of evaluating athletes.
The reason height plays a preferable quality for pitcher is the view that a batter gets of where the ball is released. The higher the release point (taller a pitcher) the more difficult it is for a bater to pick up the ball in relation to the trajectory in its downward movement.
That is the main reason that throwing sidearm gives the batter a better eye's view of the ball's release out of the pitcher's hand. The longer a batter can see the ball the better contact they can make with it.
The most ideal is a pitcher like Randy Johnson...if he threw more 12 to 6 he would be virtually impossible to hit.
It's not the speed that is important...movement and location are the best qualities of a good pitcher. If he can throw above 90 with movement and location he can be as good as Maddux. But if he can throw 90+ WITH MOVEMENT AND LOCATION AND IS 6' 9" AND THROWS 12 TO 6 HE CAN BE UNHITTABLE!!