I've seen a few revolvers in Dallas. Most are worn by officers who I can't comment on here, but who impress me as not having any sort of gun backgrounds and who probably bought the gun cheap from someone else.
I think the city security force also uses the Model 64's once used by DPD , issued to officers who didn't prefer to buy their own.
However, the officer who has the most kills in real gunfights (to my knowledge) used an issue M- 10 or M-64 (I think the latter) and issued lead Plus P HP's. He killed six opponents with that gun and load. I don't think any hit him with return fire.
I wore a S&W M-66, occasionally a Ruger Security-Six or a GP-100, over 30 or so years as a security officer. How many hours I worked depended on which other jobs I could get. I was often full time. I spent several years protecting a wealthy client who had had death threats. That job was at a large estate, where she also owned the adjacent house, with a creek behind and a wooded area with some interesting wildlife. I had to keep in mind that I might actually have to shoot someone to save my own hide as well as save other lives. And I worked bank security at a time when a very aggressive, active robber was making the rounds.
I could have carried any auto of 9mm or greater power, but I'd have had to buy new leather and magazines and pay extra to qualify again with an auto to carry one. The job paid from $7-9 an hour. If I hadn't been writing on the side, I couldn't have made ends meet. I felt pretty confident with a revolver and two speedloaders on my belt. I did carry more ammo in my car. BTW, I had to face down some would-be arsonists who were about to burn the home of a lawyer next door. The revolver intimidated them enough to leave.
By the time I retired, I was seriously considering buying new leather and mags and paying to re-qualify with my Beretta 9mm M-92FS. There are just too many crimes committed by small gangs, inc. bank robberies and jewelry store heists.
BTW, a detective with a suburban police dept. told me that he had gotten some good feedback on how the 145 grain Silvertip JHP performed in DPD shootings. It was an optional load for those preferring to carry .357's. He described the effects of that round as being very positive. He was being conservative in his description. I don't think anyone using that .357 Silvertip had to shoot anyone a second time, assuming that the bullet was well placed.
I carried that load or the Federal .357 Hydra-Shok when circumstances allowed carrying Magnum ammunition. (Indoors, I used .38 lead HP ammo.)
Some police in Europe use revolvers. I saw a pic Online of a female French detective with a snub Ruger SP-101 in a holster at the small of her back. And Manurhin has made a considerable number of their MR-88 which is based on the Ruger Security-Six. I don't think any have been imported here. It seems to use some sort of crane lock. Doesn't surprise me, as many Six series guns have somewhat loosely fitted cranes. That's the main advance the GP-100 and SP-101 offer: the front lock for the crane.
Brazilian cops usually can't carry more than .38 Special guns, so they use revolvers. Normal citizens there who don't have expensive collector's licenses are limited to .38's or .380 autos or smaller. Given that choice, you can see why .38's are popular.
Overall, today's cops carry autos for good reasons. Alas, many lack the skill and discipline to use them wisely. It shouldn't take 42 rounds of 9mm to kill one suspect, and stray bullets endanger bystanders. The Sergeant-at-Arms in the Canadian Parliament last week used a whole magazine on that terrorist. If he'd had additional terrorists nearby, where would that have left him? And then, he had to return to his office for a spare magazine!
I'm not knocking Kevin Vickers, and would support him receiving a serious award for gallantry. But I think a little bit of "spray and pray" was involved.
who work in deposit pick-ups or armored vehicle details also have a loaded 12ga pump shotgun or 2 in the vehicle. 
