The 9 mm vs .45 argument is long and tired so I will digress but the point is that a moving target is SO HARD to hit. Unless they are coming directly at you, in handgun defense situations you get your sites lined up and squeeze at the center body of mass. As of right now, the hydrostatic shock factor from a .45 is greater than a 9mm. The 9mm will penitrate more. With modern JHP they both do good jobs. However in a situation where a dude is on meth, I would take the .45. If I need more than a few shots I should have brought a rifle. I didn't mean 9mm vs. .45ACP, I meant any handgun caliber 9mm or better (more powerful). Be it 9mm, .357 SIG, .357 Magnum, .40 S&W, .400 Cor-Bon, 10mm, .41 Magnum, .44 Special, .44 Magnum, .440 Cor-Bon, .45 ACP, .45 GAP, .454 Casull, .460 S&W, .480 Ruger, or .500 S&W, any one of those cartridges will do the job. Bigger calibers leave bigger holes, so you don't have to aim a .45 as well as you do a 9mm to do the same amount of damage. The birdshot comment was a joke, by the way. I think we're both on the same page...although I could be wrong...