I may be showing my noobness, but this confused me a little. Is there different kinds of semi-auto? Because to me single shot and semi-auto are two different things, single shot meaning having to manually load each bullet into the chamber.
The next step up is burst and full auto. I always thought burst and full auto pistols(well, anything full auto really) were illegal to own unless you are a gun collector. That's besides being overkill for concealed carry and if it's difficult to take the kick from a semi-auto glock, there is no way you will be able to control a full auto pistol.
As for caliber, go 9mm. The first shot stopping power difference between 9mm and .45 is 6% and with a 9mm you can snap off more rounds easier if necessary. You can always pick up some nice hydra-shock rounds for a 9mm if you want some more stopping power. Those also tend to be more accurate than normal rounds, but end up costing $1 a bullet, at least where I live. They also look absolutely evil, which is a plus in my book.
I have a glock 26 9mm. It has a 10+1 round capacity and is pretty accurate for a pistol. If I wear my baggier pants, I can actually fit it in my pocket. That's mostly due to having a shorter grip. The g26 was specifically made to be a concealed carry firearm and having the shorter grip really helps with that.
While revolvers are smaller, they also tend to have more kick than other pistols because of their shorter barrels. If you can find a revolver that you can handle well, go for it. Otherwise I think you may need to step down to .22, but at that point you might as well buy a stun gun, imo. Or, if you can manage to get your hands on some 10% concentration pepper spray(intended for military and law enforcement.....), use that. Having been sprayed by it before, I can tell you I'd rather be shot in a non-vital area than get sprayed. Not sure how powerful the 5% civilian version is though and I don't intend to find out.
Sorry, but I have to put a vote against the XDs. My friend has a couple in different calibers and while the features make me happy in the pants, I do not see them as concealed carry friendly as some other reliable weapons, especially for people with not a lot of room to hide it or don't want to wear over sized clothing. Great pistols, just slightly too big for my tastes.
Take my opinion with a grain of salt, afterall, I have a glock 26. Obviously, ability to conceal the weapon was a huge issue for me.
Democracy: rule by the stupid