I sort of hate to add to this thread, as it's close to a religious issue... but I can speak for my own reasoning on the issue. It's the same sort of reasoning that applies to many other areas where personal experience and empirical knowledge don't suffice for a decision that nonetheless must be made:

1. I am not an expert on this subject matter. Reading is not enough, these issues would take either extensive first-hand experience (shooting people, which is experience I'd much rather not have) or careful indirect experimentation that I'm unlikely to ever be equipped to accomplish.

2. The "experts" of the field disagree. There is no useful consensus.

3. Even though the "experts" disagree, it's my skin on the line, so I have to make a decision and live with the consequences. The argument that I don't have the background, experience, training, academic degrees, military medals or whatever is completely irrelevant. Note that this is also the case in many other fields, as in choosing a martial arts instructor or which doctor to believe (I've had both tell me that I couldn't make that decision). It's my choice, and I cannot abdicate the responsibility even if I would like to.

4. While ANY direct statement about stopping power is contested, these facts are almost uncontestable:

The stopping power of the 9mm parabellum and similar cartridges has been the subject of a great deal of controversy for something like a century now. That being the case, it's unlikely to be resolved anytime soon.

The stopping power of the 45ACP cartridge has been the subject of virtually zero controversy for something like a century now.

5. Given that the stakes are extremely high, I will go with the non-controversial selection, thank you.

Perhaps it is really true that the 9mm is "just as good" as the 45, but given a choice, I'll go with the one that's almost always used as the standard for comparison.

Everyone else, of course, will apply their own reasoning to preserving their own skins, and that's as it should be... but it's well to remember that the stakes are higher than just a pet hypothesis. Being proven wrong in this case could be more than just embarrassing.

P.S. - Apropos of another section of this thread, I don't carry routinely, and haven't even made an exception in decades. That's not by choice, but in this section of The Land of the Free in 2003, doing so puts you at far more risk from the police than from criminals.