Agreed mossad However if you miss and its a big guy your done.
It doesn't always have to be about shot placement with the right caliber and load.
Read some of the data that Massad Ayoub includes in his books on tactical use of handguns for self defense.
A hydrostatic shock type of round (e.g. many of the JHPs out there with high velocity) in LARGER calibers (.357, .45...) will knock down, and knock out/disable an attacker with any torso shot that strikes an organ that is dense or has a high water content (liver, lungs, bladder, etc...).
Because dense organs are usually high in water content, and water cannot be compressed, the round create pressure waves that ricochet around the body cavities, waves of pressure, causing embolisms, and unconsciousness.
So, and med/high power 9mm that strikes a non-vital zone (I know your argument is shot placement) is less likely to cause damage that stops the aggressive activity of the attacker than a .45 in the same spot.
But, that said. If you are accurate and steady under pressure, most rounds can be a 'one shot, one kill/disable' round.
I've done speed drills and self-defense/under duress training, and I can hit torso 95% of the time at 15 yards with my .45, but not my .40 (lighter weight pistol, more recoil). I would rather hit with .45 than .40 or 9mm.
Im gonna have to go with this post. I would rather know the round I let lose down range even if off is gonna disable the person. FTR Lets all hope none of us ever have to use these skills being discused. It will change your life in a pull of the trigger.