As I've mentioned elsewhere, I've carried a handgun for about 30 years. I'm not trying to brag, just give you some idea of experience, since I'm new here. I retired a few years ago from government service dealing with foreign situations. After 9-11 I was asked to un-retire for a while. I still deal with foreign matters, but also with some domestic situations. This requires me to carry either open or concealed. I do carry a BUG too these days.
When I decided I needed a BUG, I looked around for something a bit smaller than .40 S&W or 9mm. It is a BUG after all.
About this time, I read an article in Shotgun News about a guy who carried a North American Arms .22 lr revolver for protection in Florida during a hurricane cleanup. So, I bought one.
After a while, I found that this wasn't really too good. Traded up to a Beretta Tomcat. Loved the flip open barrel but not the general configuration. Too thick and not very flat as I recall. I discovered the Kel-Tec P32 that is much narrower. Tried that for a while.
Eventually that P32 was traded for a Kel-Tec P-3AT that is the same size with a bit more punch. That is the BUG I've kept. I had a first generation that I carried until recently when I gave it to someone who needed it more than I did. So I now have a second generation version. Both have been very reliable after break-in. Actually, the second gen version has never given me any problems from the first shot.
I highly recommend the P-3AT both as a BUG and as casual carry. I normally carry it IWB in a Don Hume holster but for summer use in shorts or jeans carry, it fits nicely into the back pocket in another Hume holster. Also works well with Thunderwear.
Basically, I'd go with whatever is comfortable enough to carry that you will actually carry it. The perfect handgun sitting at home won't do you any good. I know that's trite but it never hurts to remind folks that you actually have to carry a gun for it to be of use in protecting you.