Dead is dead. Dead with a 9mm=dead with a .45. Thats all the farther that scale goes. 9mm is about 30% cheaper to buy than .45 at my local sources, which means I can shoot it more for the same dollars. Placement means more than size, and practice means better placement. That makes 9mm better, for me. YMMV, but I get two more rounds in my 9mm than the same gun in .45 before reloading, I have a 9mm so .45 means nothing to me.
It takes about 80 ft/lbs of energy to kill a human. Both 9 and .45 shoot at over 300 ft/lbs, Both are pistols. If you have serious concerns, you need a rifle or shotgun with slugs, and even there, a miss is a miss.
If you have serious concerns, you can get a 45-70 single action revolver. Lots of foot-pounds of energy but the wheels or tripod are extra