Depends
I can keep ten rounds of .22 LR inside a 4-inch circle at 30 feet, rapid fire.
There's a certain comfort in that knowledge.
I can do almost as well with a single-stack 9mm pocket pistol at the same range, but that's only seven or eight rounds, depending on the magazine in use.
That's also comforting.
I can put three or four (occasionally six) out of twelve inside that same circle at the same range from a .40 S&W, also rapid fire. The rest of the rounds make a kind of pattern out to six or eight inches.
Not quite as comforting, but still, four-to-six rounds of .40 in the ruin-your-day zone is probably adequate.
So I could carry the .22 and find that comforting, but I believe max comfort is going to be the 9mm pocket pistol.
Speaking theoretically, if I had a chance to become proficient with something in .380 or .32 ACP, I believe I'd be happy to carry one of those. I've often contemplated picking up one of those little 1907/1917 Savage pistols in .32 just to see whether I can hit anything with it. If I could, I'd add the .32 to the list.