I'm not a big fan of the smaller cartridges. If I was going to use a revolver I would want a .357 mag. For semi auto I like the .45 acp. I have heard good and bads about the .40 and would consider it. I wouldn't go down to 9mm or .380 unless it was a backup gun. I'm just not a 9mm fan but i'd be ok with carrying a 9mm uzi, i'm sure 30 rounds would get it done.

As far as a carry gun I can hide my pt145 pretty easy. It is a little thick but they had to put those 10+1 rounds somewhere.