One of the most effective street rounds (with lots of history and case studies) is reportedly the 125 gr in 357 Mag and the 125 gr 357 Sig duplicates that Mag performance and not surprisingly, has one of the highest one shot incapacitance percentages.
Road Hog is right on the money.
Real life experience at a Level 1 Trauma Center in Dallas, where we saw lots of gun shot wounds, led to one conclusion.The .357 Magnum is the ultimate handgun round with the optimal blend of speed, size, penetration and energy transfer for a 1 shot stop. Every other argument about heavy and slow vs light and fast is moot. I know that this thread started out asking about which .45 .acp round to use. I simply contend that if you want the best self defense round, get a .357 Magnum.
Ask any big city cop that has seen the results of gun shot wounds, of varying calibers, and see what they have to say on the subject. If they have had a long career and they or their colleagues have used their weapons in the line of duty, ask them about the effectiveness of the varying calibers that they and their colleagues have fired. There seem to be several current and ex law enforcement personnel on the forum. I would love to hear their real world experience. Fortunately most cops that I have met have never had to shoot anyone, but they do see gunshot wounds and the results. I got to know many Dallas cops in the ER, if they had to have one caliber as a "man stopper" they invariably will pick the .357 Magnum.
Regardless of any scientific studies, ballistic gel comparrisons or milk jugs penetrated, I'll take real world examples every time.
I also agree with everyone on this thread about shot placement. I have seen lethal .22 and .25 caliber wounds. Not exactly legendary powerhouses, but every bit as deadly with good shot placement.
Finally, regardless of how much "one shot stopping power" that you have, shoot until the threat is eliminated.
Just my personal thoughts, but I'll bet that I have seen more actual
handgun wounds than most folks on the forum and than most folks in general including the military and law enforcement folks. During my time in Dallas there were about 2000 officers on the force. They certainly weren't all present for every shooting. On the other hand our Emergency Department saw close to half of all shooting victims in the city. Level 1 Trauma Centers get the major trauma. There are only 2 Level 1s in Dallas and at my last count only 13 in the entire state of Texas (4 of which I believe are military). I'd love to hear from TABs girlfriend about her ER experience in California.