Of the two, I would pick the .45 ACP it's also known as the .45 Auto.


But I would like to recommend the .40 S&W, it's a faster round, smaller bullet, but still faster, and it was made for law-enforcement to be some kind of a brigde between the 9mm and the .44 Magnum, since the 9mm wasn't powerful and the .44 Magnum couldn't be fitted well into a semi-auto pistol, and it kicked too much.
I heard one guy on here say that he would shoot junk cars at junkyards with his pistol, and 75% of the 9mm rounds he shot at the car wouldn't even penetrate the windsheild!

So, the .40 S&W was the answer, and it's a great round.