(which is what we use in the beretta 9mm in the Marines)
Yes I know all about the ball ammo, I am Air Force. Believe me, I would much rather carry a 1911 on my hip than an M9 since we are forced to use FMJ. However, using modern ammo the 9mm can be just as effective as the 45 ACP. Most people can handle the recoil of a 9mm much better than that of a 45, so they can shoot it better. If you can shoot a weapon well, it increases your confidence, which makes you shoot more, which makes you shoot better etc.