Mostly about effectivity vs. efficiency in terms of game programming.
I wonder whether those Mindstorms balls would make good ammunition for a Lego gun. I'd normally only use 2x2 bullets in my muzzleloader Lego gun I'm making next, but those balls are probably better at accuracy. They are also very lightweight as there's only air in them. Gonna have to try that one time. Could make a very nice ammo as I have 12 of them.