This is all from memory but if I remember correctly the FBI went back to 9-mm after several studies of actual shootings and not bullets into ballistic gelatin. They found that the most important factors in a gunfight with handguns were: 1) shot placement, 2) getting the second shot on target as fast as possible. They were not concerned with killing the adversary, just stopping the fight. If I remember the charts correctly the best 'fight stopper' was a shotgun loaded with buckshot. Three 'stops' for four shots. Last place went to 25ACP which took nearly three shots per 'stop'. The main point realized from their studies was that after getting up to a 380ACP there was very little difference in stopping ability up to the main man-killer handgun round which was the 357 Magnum.
Back to home defense. I want something readily available, simple to use, and reliable as an anvil. For a high stress situation a revolver is what I want.
RSKY
The biggest reason the FBI and many other law enforcement agencies went to, or went back to, the 9 mike-mike is that many of the female agents had trouble with the 40 and simply couldn't handle the 45 ACP at all. Before then, many law enforcement agencies deemed the .45 to be 'too cruel', too debilitating, too 'unnecessary' and that it maimed too many people.
I do know the 9mm round has come a long way but it just doesn't have the 'shock' power, the knock down power, to take out a 6'6'' 300 lb bad guy that might be juiced up on something. And some people react like wounded Lions when they're hit, they get even more dangerous.
9mm hits hard if you're made of gelatin or if you're just measuring impact energy. It will definitely kill a bad guy. Or a good guy. But what it won't always do is....
...Keep him from killing you. I have a .45 and it will flat put a bad guy's butt on the ground.
They're loud, they're ugly, they're accurate up to about 2 feet (if you're a good shot) but will they ever do the job.
Revolvers are a good weapon, especially a .357; I just don't like them within a 100 yards of a kid. For some reason, every male child over the age of 3 months knows how to pull a trigger. And they will if given the opportunity. Every time. It's like genetic memory or something.
I keep a 45 ACP in one nightstand drawer and .357 Model 19 in the other. If the grand kids come by, the first thing we do is put the guns up. Except for the 45. A pre-teen kid isn't gonna chamber one of those (I keep it unloaded. Takes one second to chamber a round) All the kids in my family go to gun training before they reach 14. Even the girls.
Its not debatable. They go. If you're gonna keep guns in the house, the kids need to be taught that they're not toys.
The Black Powder rifle always gets them