Hilltop,
The most reliable handgun I own is my Sig P-229 chambered for .40 S&W, and that includes Smith & Ruger revolvers. A P-229 is pretty easy to conceal. 13 180 grain LE rounds is about as good as it gets. While I do prefer a .45 ACP in a 1911A1 handgun, I'll take the trade of having more rounds.
I'd go with a double-stack magazine. There is a tactical advantage to not having to reload, especially if bag guys are putting rounds on you. And it's wise to assume that, God forbid, you are forced to defend your life, you'll be attacked by more than one bad guy. Bad guys rarely do bad things alone. Where there is one bad guy, you can bet that his homies are nearby.
Good luck.