I'm a revolver man, and there are far more revolvers out there that are naturally small and light and compact enough to carry 24/7, than there are suitable pistols. With a little practice you can get to grip's with it double action and .38 special ammo is plentiful and cheap enough to practice with, (if you don't load it yourself). With all types of load's and projectile types.
There are those that will recite the gunfighters creed, ie., bring a gun that's calibre starts with a 4, .44/.45. Them days are gone, today the ammo is made of the best components that can be had, the quality of the firearms is first rate, reliability is mostly 100%. A little j frame S&W #36 or 60 with a 2" barrel is light and fit's in your pocket in your Bermuda's and a couple of speed loaders or speed strip's don't take up much room either.
The next question is who are you, are you a LEO/Soldier who CCW's off duty or are you just some regular guy/girl who CCW's because you are worried about your personal security?
LEO's and Soldiers should carry their duty gun or something that resembles it just smaller, just how much ammo do you think that you'll be needing? I once read that most gunfights are over in 3 to 10 rounds total having been fired, at 3 to 10 meters distance within 30 seconds or less. The regular guy/girl will not practice failure drills as often as LEO's or Soldiers do or get the regular practice required to remain proficient.
I know that some will say that the multiple BG/zombie scenario nightmare etc, what a load of crap that is, if you are being attacked by multiple assailants then you probably won't even know anything about it, and it won't matter much if you are CCW'ing or not, as you will hit the ground mortally wounded not even having had a chance to defend yourself. I hate these discussions about what gun/holster/ammo, I'm pro gun, but have been cold cocked and woke up fighting!!! So know full well that my persec is breech able.
Just my 0,02cts worth, on a subject that has been done to death elsewhere on the www.