A good question, LC. I'd choose the 9mm. I would chose that over any other center fire pistol caliber to be shot at with or go up against. If we are talking one shot (a thing 9mm proponents cannot relate to), I think I would have more chance of returning fire and/or surviving. However, if you mean emptying a magazine of 15 rounds, I would reconsider. That many rounds of anything would be a sad affair for the person shot; however the bearer of such firepower must rely on his time and ability to fire that many rounds. While he is spraying all that lead, he is receiving fire.
Earlier in this thread, someone mentioned the double tap scenario and implied it was something new. It is not. Never has been. I have no recollection of anyone being trained to shoot one round and then stop to check how that went. Good grief. Too many people rely on gun articles and periodicals to inform them what to do. I am saddened by that. Look to your own self for survival options. Go out and do your own shooting/testing. Water jugs and wet newspapers wont' tell you everything, but they will enlighten you. Shoot some actual stuff. Compare what you have decided what is best to actual personal testing. Shoot your 380s and 38s and 45s into different media. Shoot real life obstacles that will stop your bullet. Shoot steel. Wait. That's another issue. There are those who shoot at steel plates suspended and designed to swing, and they come away with the notion that the smaller caliber's inability to move the steel means nothing. We've been led to believe that crap. Fire different calibers against steel. Note the impact and the resulting movement of steel. Not a measurement of a round's potential against flesh, you say. That's because you've bought into the gun rag hype that such shooting proves nothing about a round's performance against a human assailant. I will agree steel is not all inclusive; it does not indicate projectile reaction to ballistic jell or flesh. But it does prove incontrovertibly what caliber exerts the most force. And if you believe that is of no consequence, you are simply foolish. Shoot said steel with a +P 38 and after it the plate ceases its pitiful swing, shoot it again with a .357Magnum. Shoot it with your 9mm, then again with your .45.
Not sufficient evidence? Fire the lesser caliber into anything at all and observe the difference. I don't believe we can any longer label the .45acp as slow and heavy. The modern ammo tested against lesser calibers clearly show which is superior. Which begs the question, the eternal question, do you as an individual understand that if you favor the nine for its low recoil, higher capacity, cost of ammo, and most of all the ingrained belief the nine is best because everyone else likes it, then you are (I'm sorry in advance) you are weak. This is me, a slim non-muscular female, a person of less physical stamina and strength than most men--the little petite girly sissy who has gleaned from the previous post that I can shoot a 1911 better than you men can your little nines. I can do with my 45 what you cannot with your nines--that is stop an opponent with three times less rounds than you can.
The saddest part of this entire thread is that I must take from it the fact I am more proficient with big calibers than you are with the little ones. Also, that you are in doubt as to what you would be capable of when called on to fight.
I am outspoken; some of you can't accept that from a female. I think you base some of your opinions on the lie that a girl cannot know more than you about what has always been a masculine subject. No way can a female be more assertive or confident. No way will you heed her advice. It is automatically incorrect.