In close quarters an attacker can push a slide out of battery, and you’ll never get a round off. Can’t do that to a hammerless revolver.
If you are in a close quarters encounter, you've just violated the first rule of close quarters combat...maintain situational awareness so you don't find yourself in a close quarters encounter. As for me, I'm much more concerned about running out of ammo than I am about my pistol being out of battery. There are countermeasures you can take to get back into battery. Reloading a revolver in the middle of a close quarters encounter ain't gonna happen.