I’m a NRA-Certified instructor, and we always teach our students that a small revover (say, a .38) is best for concealed carry. In self-defense situations, the average distance an attacker will have to cover to get to you is 21 feet. How long will that take? Less than 2 seconds. You have to ask yourself if that sexy semi-automatic will fire. If it doesn’t, you will have to chamber another round and try again...but the problem is..your assailant is already on you. With a revolver, just point and pull the trigger, if it misfires, pull the trigger again.
Now, chances are that a good semiautomatic won’t misfire, but are you willing to bet your life on it?
Also, the magazine capacity of a semi doesn’t matter much. If you have to shoot more than twice, you’re going to be dead anyway.
Most self defense encounters are well under 21 feet. However, happily, MOST bad guys want to break off when they see a gun pulled. Those that charge you are hard core and probably on drugs.
Unfortunately, as OldPossum points out, NO HANDGUN will stop that person in his tracks unless the bullet shreds the brain. Even a 44 Mag with a direct hit to the heart will leave the BG with 10-15 seconds of useful consciousness to attack with a knife, shoot you with HIS gun, etc.
(see the FBI article here, page 8: http://www.firearmstactical.com/pdf/fbi-hwfe.pdf)
Therefor, your choices if charged are 1) shoot and move, 2) wait until very close and chance a brain shot, or 3) shoot, but prepare for hand to hand (or a brain shot at 0 feet).
As for semi-automatic reliability: they are great if you have checked out the ammo first. Many semi-automatics will fire thousands of rounds without a hitch. Some have ammo they don’t like, and you need to make sure you are not using that type.
However, I think the large number of rounds is overrated. As I said, if they don’t run at the first shot or two, and don’t drop immediately when shot (the FBI paper explains that as well), then you have to expect them to shoot back - and one round in the right spot will kill you seconds after they die.
I use a 5-shot Model 60 .357. One round to the chest, then one to the face. Remember George Adamson’s advice on killing a charging lion: Wait until 10 feet, and don’t miss.
Except for home defense, I want to shoot once - no more than twice - then move.