I'm not asking for which sidearm to mount it on, I'm asking in general about it. Is it being utilized for it's ability to zero with drift and elevation? How long is the battery life on each model of micro red dots, or does it matter at all? I already know my next purchase will either be an M&P 9 or 45, but will this sight set be compatible with them, to use for JIC the red dot all of sudden, becomes inoperable? Or is the sights being used to co-witness at all?
I will speak to my own experience with an RMR on an M&P w/milled slide...
I went with a pistol mounted MRDS setup because of my aging eyesight and cross-eye dominance (right handed, left eye dominant). After a lot of range time and dry fire practice it's much quicker and easier for me to pickup the dot than to get a proper sight picture with the "irons". The dot does sort of cowitness with taller (suppressor) sights. In my case, the dot floats just above the top of the front sight.
I went with the green dot, dual-illuminated RMR. There are no batteries and fewer mechanical parts to fail. Plus it's built like a tank. You can see all sorts of videos of people whacking their slide mounted RMRs on tables and 4x4 posts repeatedly without killing the sight. If I did manage to kill it, the irons sights are visible through the window of the RMR. It's basically just like a lower 1/3 cowitness with an EOTech on an AR.
The green dot doesn't wash out as much as the regular amber dot can. I also went with plain black suppressor sights so I wouldn't have a bunch of green dots (one in the RMR and three more on "night sights") cluttering up my sight picture.
As a side note: Typical "suppressor sights" still aren't quite tall enough to see over the top of my Gemtech Multimount. It's not a big problem, but the MRDS has the added bonus of getting my aiming point (dot) up above the can so I can actually see it on the target.