I am not LEO, but I carry everyday for the lawful defense of self and those under the mantel of my protection. 9 out 10 times, it's either a Ruger GP100 Match Champion with full-tilt 125 gr. Magnums, or a S&W .41 magnum with 210 gr. Speer Gold Dots.

That said, if I were an LEO today and had the choice, I would probably choose a VERY high capacity bottom feeder. Probably a Beretta 92 with a 20 round magazine. Massad Ayoob has written extensively on collecting stories of LEO's and armed citizens who lost gunfights BECAUSE of the capacity and reload issues with revolvers. There are quite a few cases.

I carry a large revolver b/c I am not as likely as an LEO to find myself in a protracted firefight with multiple armed felons who don't want to go back to the big house. I'm in a rural area with very low crime; so wheel gun it is for me.