My personal preference is for the Safariland Comp II speedloader, that's what I used in competition for years, some others used the Comp III or the Jet Loader. I also carried the Comp II's on duty, it was the only speedloader I would use, I carried Safariland Comp I speedloaders to go with my Chiefs Special for concealed carry. I have never known an officer to carry HK speedloaders, or use them in competition, civilians are the primary consumer of the HK speedloader.
Quite frankly, the primary use of a speedloader is for self defense or competition, there is really no compelling reason to use one outside of those uses.