...it makes no sense to use anything more powerful than the absolute minimum, since it would just slow you down.
It makes all the sense in the world to the guy that wants to adhere to the spirit of the game rather than taking every advantage just to win a match. To me, what matters most in CAS is not whether you win or lose, but how you play the game. Gunfighters, cowpokes, outlaws and lawmen in the late 1800's did NOT look for the lightest calibers to throw the most shots downrange in the shortest time, completely disregarding their effectiveness. Neither should we.