From everything I've read shot placement is more important than cartridge selection.
The second most important thing to realize, IMO, is there is "no" pistol cartridge that absolutely assures a one hit stop. There is at least one case on record of a guy who checked into an emergency room for treatment 3 days "after" getting hit by and carrying around 3 (three) 44magnum hollow point bullets (that stayed in his body). There are other cases of folks needing 6 or 8 hits by a 45 to be stopped. Lance Thomas, the LA watch store owner, frequently had to hit invaders to his store with 3 to 8 shots to get them to go down, even when he was shooting a 45. (If you haven't read about Lance Thomas, you have an entertaining read ahead of you.)
When I was picking a caliber as part of my research before I start carrying, I read all three of the "stopping power" books. Some background: I'm a retired Space Power Systems engineer, I'm used to data, lots of data. Of all that I've been able to find, those three books gave me the best understanding of what the incremental performance improvements might be related to cartridge and barrel length. I don't spend a lot of time worrying about the exact percentages - things within 5% of each other are effectively the same in this sort of subject.
Folks seem to love or hate Sanow, et. al. for what they wrote, and all the work they went to doing it, but their approach which balances actual shooting performance with laboratory test results is better than any other I've read about, at least an engineering sense. They also include several chapters by others on the FBI and INS testing that are quite informative.
That said, beyond ballistics, there are psychological and other factors including the effects of drugs that can have as much or more influence the attackers ability to do you harm as cartridge selection. The person shot may at some point die, but it may be after they have a chance to finish their attack.
You ask a good question, and while the answer is most likely an unknown confluence of factors, some of which may not even have been identified yet, it sure a learning experience to discuss it.
FWIW: After shooting everything and a variety of pistols, I ended up picking 9mm first, Glock 19 second (because, in order, it fit my hand the best, has a reputation for being as reliable as gravity, was pick-up and fire like a revolver, held at least 15 rounds, was a decent all around size and weight, and had a rail). I can shoot a 9mm significantly better than an S&W40 or a 45. By better I mean I can hit what I'm aiming at much better, much smaller groups, and make faster accurate shots with out much increase in group size at the combat ranges of significance (25 yards or less). In going for better shot placement (the most important factor) I was only giving up 2% to 4% in stopping power over a 40 or 45 so that is what I went with. I may at some point add a PM9 to the carry list, but for now I'm a one-gun guy. I've been training by firing about 200 rounds a week.
I really believe that shot placement is the most important part of stopping power, so I'm putting my time on improving my ability to do that.