When a medical professional talks about bullet placement being the key factor, you have to remember that he's not talking about shooting a "tight group" at the range. We're talking about the very specific body structures that the bullet hits or passes by close enough to disturb through hydrostatic shock. This is a matter of millimeters, possibly centimeters, but not inches.
So while shooting a 4 inch diameter group right over the X ring of your silhouette target is great, inna man some of those shots through the X ring may not hit the specific nerves and organs that are needed to stop your adversary.
Skill with your firearm can cause you to have accuracy within inches. But really it's a matter of luck whether your bullets are on the correct course --millimeter by millimeter -- to hit what they need to hit.
THEREFORE I favor shooting multiple hits as rapidly as possible, rather than counting on a one-shot stop. The more tickets you buy in that lottery, the greater your chances of winning!
But there's a limit to how far I would actually bet my life on this information that I have been told and or deduced from years of study on the subject of stopping power of handgun bullets.
I "say" that having a rapid-firing semi auto gun in a modest caliber should be better protection than a very powerful magnum that holds fewer rounds, but in real life I don't know that I would choose a 12-round self-loading pistol in 380 caliber over a six shot 44 magnum revolver.
It was made more in jest, as I have a thread discussing the viability of carrying a PMR30 for concealed carry. Hardly any recoil, extremely accurate, and packing 30 rounds of .22Mag ammo at barely 19oz seems like it could be viable on paper, anyway...