Just about any firearm will work for self-defense. If you are concerned about "knock down" or "stopping" power, .380 ACP is pretty weak, but I don't think an assailant will keep attacking if he/she/it gets shot by a .380. It will be good enough. Hell 22LR would be good enough, most likely.
I keep my 9mm loaded with range rounds because they are cheap and reliable. I know they are not as good as defense rounds, but again, I doubt an attacker will keep attacking after I plunk his/her/its ***** ass, so it's good enough for me.