if you want proof, the easiest way to do that is go to a game and ask everyone with a different kind of bb if you could have one for compariosn test. I'd imagine you'd get alot of different kinds so long as there is no field bb's only rule. Honestly I think that'd be the best way to do it and not have to buy 10 or more different kinds. I have never used crosman bb's though so I couldn't tell you if they are any good.
Bastards are best IMO and many other players feel the same about them.