"Some experts will say it's barely adequate, and others will say it's barely inadequate." -Massad Ayoob

I'm kind of on the fence regarding the .380's suitability for self-defense purposes. If you gave me the choice between a Glock 42 and a 43, I can't think of any scenario where I wouldn't choose the 9mm. There are some really tiny .380's that are a delight to carry, but I carry a gun because I believe there is a realistic chance that I might have to use it to defend my life and the lives of my family. I honestly would not feel all that comfortable and confident with trying to do so with a 10 ounce .380 that only holds 6 rounds.

A high percentage of the really small .380's seem to suffer from reliabilty problems and are usually pretty finicky about what ammo they'll accept. The ones that are shootable, handle well and seem to run fine(like the Glock 42) are minimally smaller than currently available small 9x19's, which I view as being substantially better suited for defensive use.

YMMV