I found this usefull, I just cut and pasted the end but will add the link to the entire article. It kind of agrees with what most have ben saying,
Conclusion and Thoughts on 9mm vs. 45ACP:
It is my belief based on data from serious researchers that with FMJ, the 45-caliber automatic is more potent than the 9mm. That does not mean that I believe either to be anywhere near the top of the list for self-protection. I do not believe that "they all fall to hardball."
I do tend to agree that the expanding defensive bullet should penetrate between about 12 and 14". This may be more than required for a straight on, unobstructed chest shot, but it better insures punching the vitals should an intermediate target like an arm get in the way. It would also likely be more effective if the shot was made from the side rather than the front or back.
I am convinced that the size of the wound channel from an expanded .45 ACP bullet will be larger than that from the 9mm and this should make it more effective, but I have not seen a noticeable difference on animals as mentioned previously. I am equally convinced that gelatin results may or very well may not match what actually occurs in flesh-and-bone targets.
Probably the most important factor in stopping power (regardless of caliber) remains placement. That this can be difficult to obtain in the life-and-death fight scenario doesn't change the necessity for it if we want the opponent to go down for physical rather than psychological reasons.
With the best loads, I opine that .45 ACP is a better "man stopper" than 9mm with its best loads, but am not sure of by what margin.
I do not believe that a 9mm loaded with the better loads is an inadequate defense gun and frequently tote one myself.
I do not "trust" either the .45 ACP or the 9mm (or any other handgun caliber) to provide the elusive "one shot stop" unless the brain or central nervous system is destroyed.
I am not convinced that the temporary cavity produced by handgun bullets is totally irrelevant, but I also have no idea of how it may actually contribute. I wish there would be more serious research in this area.
Either of these calibers with any load may fail to provide the desired results even with a "good" hit. Either may require multiple "good" hits.
Perhaps either caliber would provide fewer failures if we practiced as much as we worry about our caliber's stopping potential.
I believe that we will continue to see stunning successes and dismal failures with all commonly used defensive handgun calibers including the 9mm and .45 ACP.
An experienced old lawman once told me that a man can be the easiest or the hardest "critter" to put down and the problem is that you never know which you're getting. I think that maybe what he was trying to say is that while a man is an animal, wild animals are not men. If a man is shot and thinks about what has just happened, his human drive to survive may include stopping what he's doing or begging for help. A javelina or deer or bear, etc will not stop until it physically can do nothing else. On the other hand, if a shot man simply reverts to some primordial anger or rage (I'm not sure what to call it) and simply lets his animalistic side come out, he may very well be a most difficult opponent. For 200-lb. animals, we sometimes see even high-powered rifles fail to provide instant "stops." I do not know how to factor in the adrenaline dump that can occur when we're suddenly injured or realizing that we must fight to survive, but I do believe that all of the preceding can play a significant role in the area of stopping power.
here is the link to the entire article, he has done a lifetime of hangun shooting and hunting with 9mm and 45 cal, and I thought some may find it a good read regaurdless of your particular view. It made me more open twords the 9mm than before I read it.
http://www.hipowersandhandguns.com/9mm vs 45.htm
