I'm not a hunter but, in thinking about your comment, it stands to reason that you would not want to use a heavy guage shotgun (e.g., 12-guage) to hunt small birds like quail so as not to 'atomize' them.
Well, no. You do it because it's a bit more challenging or you prefer a lighter recoil. The 12-gauge doesn't hit the bird any harder, the shot pattern is simply bigger and there's more shot in it. Unless you manage to hit the little bugger before the pattern has spread, that is, in which case you're reeeeal close.
What you do do is adjust the size of the shot you're using to fit the size of the game. You wouldn't hunt geese with number 9 shot, nor would you hunt quail with number 3. That would atomize them.