Tn, my issue is that the fellow's assertion that it was 'hard to miss using a shotgun, making the shotgun the number one' (or to that effect) was something that eliminated this fellow from credibility for me. The bad part is that he was correct in that placing followup shots with a 22 is easier, but if you can shoot worth a dang the single shot from the .45 is a better fight stopper than 3 or 4 shots from a .22 when considering that you have no control over where your attacker will be or what he may be wearing when you attempt to defend yourself. I have first hand knowledge that a .45 in the chest beats a .22 in the chest. Also, aiming a .22 at someone's head is pretty good to demonstrate intent to kill, when a .45 to center of mass is not the same demonstration of intent. Ask an attorney, if you doubt me. I would rather select the weapon that I know for sure will do the job, even if the guy is wearing a coat or is behind a board.
Now, as far as the 22 mag goes, having only fired them at squirrels (and vaporizing them, literally) I have no thought that there is more power to them relative to the .22 LR. I also have to agree that the gun you carry is infinitely more powerful than the one you do not. Also, I must state that from personal experience, looking at a pistol or revolver from the business end makes caliber selection psychologically moot if you are not prepared for the experience. Your brain says "I am about to get shot" and your instincts tell you that you do not want to experience that. As most crooks bail when confronted with a gun, it is somewhat academic what gun you have, provided that you actually have it WITH you! So if the .22 is the one you have with you, it is the one you have, so is better than nothing. However, when shooting someone with such a small diameter bullet, even at .22 Mag velocities, keep in mind that if you could carry a .45 as well, the .45 is going to be a lot more effective at stopping the fight physiologically RIGHT NOW, than the .22 that does not stop it yet kills the guy three days from now. You are still dead, even if he dies later. The point is to keep you from getting dead NOW. The .45 wins again. Just sayin' is all...