I carry a single action revolver from time to time. A Ruger Lipsey's Blackhawk 45 Colt / 45 ACP convertible. Usually carry the 45 acp cylinder, because it's easier to reload from a 1911 mag and there is some great defense ammo available in that caliber.
For AIMED shots, I think a single action revolver can certainly rival a double action for speed and probably beat it for accuracy if the shooter has a high level of familiarity with the single action revolver.
As regards being deemed a "cowboy" by a court, I'd rather have someone think I'm a cowboy for carrying a six-shooter, than an active-shooter because I'm carrying a high cap auto.
I also agree with Ozzieman. I think I'm going to run out of time long before I run out of ammo.