I think the general point being communicated here is that where a bullet ends up is vastly more important to the end result than what type of bullet (providing we are discussing service calibers here) is used. The potential effect of a good shot can be maximized using modern JHP that penetrates deep enough to hit vital structures and expands reliably to cause as much damage as possible.
Given that handguns are limited platforms it makes sense for those of us who are interested in using a firearm to stop the hostile actions of an attacker to focus on selecting a reliable platform in a reasonable caliber that we can best use to put bullets exactly where they are needed under the stress of a life or death encounter. Using myself as an example, I can shoot an M&P in 9mm under stress better than I can shoot an M&P in .45 ACP. Thus it would be irrational of me to trade in the performance I have with the 9mm version of the M&P solely to gain the little bit of extra permanent crush cavity offered by the .45 ACP. In reality my efficiency (measured by speed and accuracy) with the 9mm is more likely to provide a measurable difference in the fight than the bigger bullet.