I carry a S&W 637 (Airweight Chief's Special).
Reasons (in no particular order):
1) Weight. I'm more likely to have a gun that's comfortable to carry on me if I ever need it (hopefully, I never will need it)
2) Accuracy. I have fairly small hands, it fits them better than any comparably sized 9mm I've found (and I don't want to carry a .380)
3) Adequate firepower 5 shots, 124 gr Gold Dots in .38 spl +P - yeah, I know it's slow to reload, but what are the odds I'll have to? If you have to fire more than 5 shots, you either need more practice, or you need a shotgun/assault rifle. Knowing I only have 5 shots, I think, will make me more deliberate (safer for any non-BG's in the vicinity).
4) Reliability. That's been covered. As to the question someone asked about why you would want to fire through a pocket, I can only give you the information I was given: 90% of gunfights occour within 20 feet, 75% within 5 ft. Grab a friend, go buy a toy pistol, and play this little game. Take your toy pistol, put it in the holster and cover it up. Measure 20 ft. Have your friend close that distance as quickly as possible (he moves first - this is a defensive drill, right?). Try to draw, point and pull the trigger before he reaches you (if you want a little realism, give him a rubber knife, wiffle bat, or let him try to tackle you). Then try it again at 10 ft, and again at 5 ft. See how many times he's on top of you before you can do all that. Then remember - you might not know it's coming when it's for real - cut the time you have in half.
5) Simplicity - I pull the trigger, it shoots. If I have a bad round, I pull the trigger again. That's about as simple as it gets
6) Safety - it's easy to see if it's loaded with a glance.
7) Reliability
That's about it. I like autos, too, but my choice for a carry gun is a revolver.
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Beginner barbarians probably had the idea that every house they broke into would be full of untouched loot and frightened, unarmed victims. It just doesn't work that way, my friend.
I hope these evil men come to understand our peaceful ways soon - My trigger finger is blistering!