The more air in the ball, the further it will go. At least until the pressure is pretty high, this is not a big surprise and based on more pressure making the ball more "elastic": if you hit a floppy volleyball, it deforms a lot and in part without bouncing back into shape, thereby absorbing some of the energy of your hitting it by deforming, which would be "plastic" behavior.

On the other hand, a well inflated ball will deform for a very brief moment when you hit it, but then the pressure inside makes its wall bounce back into shape, propelling the ball forward and away from your hand.