Some further points in the continuing caliber religious wars.
1. It is not clear that .45 ACP has significantly better stopping power than 9mm Luger, depending on what you feed your gun. According to Ayoob, "Independent studies by Sgt. Evan Marshall and this writer indicate approximately 68% and 70% stopping power capability with one round of .45 hardball; both found the better 9mm hollowpoints to have virtually identical stopping power. These figures came from documented street shootings of armed human beings, not from laboratory experiments in "test media".
What I have read indicates that 9mm guns are more likely to accept JHP with a higher degree of reliability than will 1911s. And if it matters to you, .45 ACP also seems to be much more likely to penetrate, keep going, ricochet, etc.
2. Studies indicate that veteran LEOs in street gun fights hit the target with about 60-65% of shots from a semi-auto (about 25% hits from a revolver, which is why no one uses wheel guns anymore). That means in a full blown shoot out, you can put about 4 rds into (or through and through) a BG, while you can put about 10 rds of puny little 9mm into him. More importantly, if you've got two BGs, you can put 2 rds of .45ACP into each or 5 rds of 9mm each.
3. Being comfortable and competent and confident with the gun and the ammo is probably as important as what you are shooting. (I don't even want to hear about your .22; there are limits.) A couple of goods hits with 9mm, even hardball, beats spraying .45s all over the landscape.
That's just my opinion. I may be wrong.