Cleary you've never seen my "3 P's" mantra
Practice
Placement
Penetration
In typical self-defense scenarios
Using common service caliber handguns
The 3 P's trump all of the common arguments
Except for the fact that an assailant isn't going to be a piece of paper, stapled to a stationary stand. More likely a moving, jumping, running, slashing, stabbing, kicking, grabbing target.
That's when Murphy's law trumps all the training you have under your belt.
Not to say that practice isn't needed, or helpfull. But in the final result, luck has almost as much to do with hitting that tiny area of the spine that will immediately incapacitate a human as all the practice, and training.
Without that perfect hit to the CNS you are then hoping for one of the less sure ways that a human is incapacitated. Physical pain from being shot. In which a more destructive item passing through tissue would be helpful. Or mental shock from the fact they have been shot. Again, more tissue damage than a small hole poked through could be helpful. But maybe not. Mental shock, fainting, can be seriously effected by state of mind, adrenalin, or drugs.