There’s a myriad of issues which will forever carry this “discussion” forward.
Naturally, the most prevalent is the American culture of “bigger must be better.” Regardless of whether “bigger” actually can or ever is proven “better,” or despite the fact it is proven that bigger is NOT actually better. As is the case here - it’s been proven, bigger is not actually better.
Equally, the global predisposition to not understand technical or statistical analysis at any level, and a general popular refusal to put forth effort to do so. If data is difficult to understand AND the conclusion violates my personal belief, then I can plausibly dismiss all of it as long as I don’t try to understand any of it...
And of course, there simply is no mechanism to independently prove or disprove any given hypothesis in this discussion. Is a 9mm better than a 45? Or vice versa? Well, design an experiment. Have a thousand people attack you, and dispatch half of them with 9mm’s and half of them with 45’s - then maybe we’ll know. Pretty ridiculous. So instead, the only real world data we can cite are threefold: 1) ballistic data, 2) empirical results in controlled experiments using simulated media, and 3) extremely varied data from inconsistent and uncontrolled real-world defensive shooting events. Of these, the first two data sets appear to have the greatest integrity, but obviously have the least validity and applicability, whereas the 3rd data type is highly valid and applicable, but the integrity is challenged by the nature of the incredibly varied sample set. No two real-word defensive scenarios are alike, so the analytics rely upon a massive dataset which must be normalized for comparison.
Which means collection of the data is exceptionally burdensome, which in turn means collection of such a dataset with any quality is exceptionally rare. But there are a few, and the results tend to point the same direction:
A vast majority of folks believe in an advantage of heavier bullets and more power in a defensive handgun, but unfortunately, this popular opinion simply isn’t justified or supported by the real-world results.
But even knowing this, being so “woke,” I carry a G19 whenever I feel my risk profile is heightened, instead of an LCP, and have resorted to carrying a P224 in 357Sig in certain risk scenarios as well... all the while recognizing the hypocrisy and silliness in “up arming” in these different risk exposures.