Based on my experience, not someone else's controlled tests, the revolver is more reliable than the semi auto. I have fired thousands of rounds out of both. Bottom line is more malfunctions with the autos. My guns are kept reasonably clean, usually clean at approx. 200 rounds. I'll point out the even the M-14 rifles we trained with would stop working if sand entered the picture. M-16s were totally turned into single shots if you had a cleaning rod to poke the empty out, totally useless if you didn't have the cleaning rod. Revolvers do fail just not as often as semis. I do have a couple semis that haven't failed(jammed) yet but it's just a matter of time. If nothing else a substandard round will cause it to jam. Dropped magazine at the wrong time, bottom fall out of the mag, ejector break, shock buff will fail(do not use them in a carry gun), ejector break, all the while a revolver will probably fire all the rounds in the cylinder except for a bad round of ammo and then you can usually pull the trigger again and it'll shoot the next round.
The only thing a semi does better than a revolver is that it holds more ammo.