Think of it this way -- you carry a gun in case you get into an all-out fight for your life and the lives of those you love. Carry something you would want to have in a gunfight... i.e. whatever you can best get hits with and that which holds the greatest amount of ammo. Carry a full size double stack if you can -- if not, carry the largest thing your situation and need for concealment allows. Try for a double stack if at all possible, and go 9mm instead of .380 if at all possible, and striker fire instead of double action only. I'm not a fan of the Glock 42, because there are pistols that small and smaller in 9mm. You can have vastly better performing self defense ammo with 9 than you can with .380. Wih .380 you either get adequate expansion or adequate penetration -- not both. With 9mm +p, you can have it all.