The 9mm only kills the body. The .45? The .45 kills the soul.
The lighter 9mm decelerates faster, so is more likely to transfer more of its energy to the target and less likely to over penetrate.
Now that's settled, we need another debate. Glock or 1911?
In the October issue of Gun Tests, they compare 9mm and .45ACP. They look at bullet expansion, penetration depth and recoil delay.
Their bottom line? The calibers and cartridges are pretty close. Don't worry about the difference.
.45 ACP wins in expansion, .45 decelerates slower but 9mm recoils less. And guns generally hold more of the 9mm.
The 9mm Luger Speer 124-grain +P Gold Dot hit with an initial kinetic energy of 423 ft-lbf, while the 45 ACP 200-grain +P Gold Dot hit at 440 ft-lbf and the 230-grain Gold Dot impacted at 311 ft-lbf. The expanded diameters were nearly the same, but the 9mm was lighter, so it decelerated more rapidly than did the 45 ACP.
So which is better: 9mm Luger or 45 ACP? The answer is that they are functionally identical — the target will not know the difference because the difference is so small. They are certainly better choices than the 380 ACP or 38 Special, but no cartridge will ward off evil spirits or drop a guy with a near miss.
I actually prefer an .88 Magnum.
I do.A better question is will you carry it all the time?