I’ve always been concerned about relying on the .380 for self-defense. It just doesn’t carry a lot of energy. While it is a little lighter on recoil then the 9×19 it carries roughly half the energy. Further I’ve never had a shooter that couldn’t handle the difference in recoil from a .380 to a 9×19. On the opposite end of the spectrum the .45 acp carries a lot of energy and its ability to knock an assailant off their feet regardless of what their wearing or what their using (pharmaceutical wise) is well attested by both the military and the police forces around the world. Aside from that it is a bit more recoil then lighter shooters and recoil sensitive shooters want to shoot. The .40S&W is a great compromise as attested by both its bullet mass and muzzle energy. But there is a price to be paid for this compromise (literally) as the ammo isn’t much cheaper then the .45acp. I’ve commented before that a .22lr in the hands of a well-trained and practiced marksmen will serve better then a .50bmg in the hands of someone with no clue. While that may be an exaggeration the ability to be able to afford to practice as often as possible is a big consideration. The 9×19 due to its popularity shines in this regard and is overall the cheapest round to fire. The 9×19 does have a few problems in that its fairly small and fast moving giving it a relative lack of knock down power compared to the .40S&W and .45acp. But from a purely numerical comparison I think it’s the best of all compromises. It is also widely available and if you’re ever traveling and need ammo it can be found at literally any sporting goods store. The 9×19 is also found in most popular models of handgun from subcompact to target size barrels. For people with weak grip strength that have trouble racking a semi-automatic handgun the Smith and Wesson M&P Shield EZ is a very good option.