SC, Ruger makes a really thin .380, and the 9 mm version is only slightly bulkier. But a .380 doesn't have much stopping power, though it's definitely better than not being armed. Semi-autos can be prone to jamming though, and if that happens your goose is cooked. Semi-autos will also be the first types banned by the Hildabeast.
But my main problem with semi-autos is their complexity. You ideally want to keep a round in the chamber, but then the safety has to be on and/or the gun on half cock. Then to shoot you have to flip off the safety, which is a distraction (although a split-trigger safety is one way around that problem).
Alternately, you can carry the gun with the chamber empty, but then it's useless until you pull back the slide to chamber the round, which is time consuming and distracting. Then once the round is chambered, the hammer will be fully cocked and precarious, so you either have to shoot or else carefully hit the de-cock lever to go to half cock. And when you do shoot, you have the same problem once you're finished firing - the hammer will be fully cocked and precarious, so you must de-cock again. All in all way too complicated in a life or death situation.
Some semi-autos have features that uncomplicate things, split trigger safeties, internal hammers, etc, but there's still the jamming problem. Personally I'll take a revolver any day - no safety, no slide, no de-cock, no jamming, and you're not vulnerable to anti-gun legislation.
Revolver rounds are also far more powerful than most semi-auto rounds. One shot from a .357 or .38 Special +P hollow point will neutralize your target. There are some semi-auto hollow point rounds available but they generally don't feed as well and increase the chance of jamming.
My philosophy - keep it simple, and it doesn't get much simpler than a revolver. S+W has the 'Air Weight' alloy .38 Special +P which is small and ideal for carrying. Not as thin as the Ruger .380, but packs far more stopping power, and you just point and shoot.