I can't think of any topic where so much hot air meets so little actual experience as "which caliber is best?". Scary news channels nonwithstanding, people just don't shoot people often enough to be able to have an experiental basis for declaring which caliber works for them and which doesn't; even Jeff Cooper didn't.
Compared to some of the people who purport to tell us which round is "best", I found this guy's video pretty refreshingly straightforward. Instead of trying to explain which round is best, he gives a number of fairly common sense reasons why the .45 ACP isn't. I can't say that I disagree with him on any of those. The .45 is an excellent defense round, and back a few decades when any but FMJ bullets had reliability issues in semi-autos, it was without doubt the only choice if you needed more "firepower" than a revolver. I carried cocked-and-locked 1911's for many years (Colt, Para-Ordnance, S&W), as well as a Sig P 220 for winter outdoor carry. But it is indeed hard to make the argument today that the .45 is the "best" choice for any reason, which is all he says.
There is one argument for the .45 he leaves out, the psychological one. That big black hole somehow looks a lot more threatening than a 9mm when pointed at you. And after all, the best gunfight is the one you win without having to actually pull the trigger