No common combat handgun round is a completely reliable manstopper.
Evan Marshall (I don’t know if he’s still in circulation or not; he used to write articles (frequently on stopping power of combat handgun rounds) in firearms periodicals) related a couple of glaring failures to stop with .45 ACP. In the one, two thugs attacked a man and his wife. So hubby drews his .45 and double-tapped thug #1 in the chest. He turned to engage thug #2, when his wife cried out because thug #1- with two bullets in his chest- stabbed her with a knife. So he double-tapped him again, and the thugs fled. He rushed his wife to the hospital (they were able to save her), in walked thug #1 with four rounds in his chest.
In another case, two perps gunned down a cop with a total of five rounds of .45 ACP. They were laughing and congratulating themselves and not paying him any attention when he struggled to a kneeling position, drew his service .38 Special, and dropped both thugs- with 158-grain semiwadcutters, no less.
Is .45 ACP a more effective and generally better defensive combat round than .38 Special? Yeah, certainly. But I also agree with CSB when he effectively said that it’s better to have a .38 you can handle than a .45 you can’t.