Well, no matter how well these balls are regulated for pressure, they ALWAYS be slightly different due to temperature, wear of the game, and any other out of round issues. I don't know what the specifications of a #5 soccer ball is, but I suspect that it isn't anything like a precision ball bearing.
As for other varuation, just think of the varying friction of their surfaces as they are used more. Thier new shiny covers will get dusty, scratched and marked as robots pick-up, scoop-up, run over, dribble, roll, and otherwise "fold, spindle and mutilate" the balls during a match.
(yes, I know, you can't damage or destroy the playing field....but I'm talking about normal wear and tear.....as you see with real soccer balls after they are broken out of their store packages.)
I love the idea of a ball shooter........but....
