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.