Both are extremely reliable weapon systems. Any revolver is traditionally more "reliable" than any given auto handgun. However, when considering the glock family of firearms, you don't get much more reliable. The real question is, do you prefer the slightly more reliable 5-7 shot revolver over a 12-19 shot auto that has a reputation for taking some ridiculous beatings and still function rather flawlessly.
In the end, for CCW, it all comes down to shot placement and number of attackers presenting themselves as targets. As a 10 year military combatant, trust me, you can have all the confidence in your shooting ability in the world, but when tensions flare, and a human target/targets are standing before you, shot groups usually go down the tubes.
I consistently qualify as an expert marksman as well as hold the title of designated marksman in my unit. That being said, I still prefer higher ammo count and I'll take my glock 23 with 14 rounds (+ spare mags) over any revolver, any day of the week. Any weapon system can fail. Proper maintenance and quality ammunition will minimize the possibility but never eliminate it completely.
That's my two cents, but never discount the perks of a solid revolver. After your 6 shots are up, they still make a pretty decent club to bludgeon your attacker with