The caliber I choose for protection is 380.
I have other choices available, 32S&W 38S&W, 38Special, 357, 9mm, 9mmMak, 44Special, 44Mag, 45Colt, 45acp.
I have the handguns, the ammunition, the experience, the holsters for any of those.
Yet what I carry is one (or more) of the small 380 pistols.
When I do carry one of the other choices I will also be carrying one of the small 380 pistols.
I've been shooting handguns since Ike was President and my first 380 was probably while JFK was still in office.
But today's pocket 380s are smaller and lighter and slimmer and easier to maintain than the Beretta, MAB, Browning or Walther of the 50s & 60, as or more accurate, with more efficient ammo than we could buy back then.
Does that make a 380 "really" an adequate self defense gun?
For me the answer is "Yes". I can shoot them well, maintain them easily, conceal them is most any clothes and all over my body. I find them easy to present rapidly, shoot rapidly and accurately, relatively inexpensive to buy and maintain and as reliable as any handguns I have now or have owned in the past.