I first started playing around with a RDS on a pistol back in 2010. I slapped a J Point on a rear sight mount on a G19 and took off for a RskTkr Consulting class in Ohio. The setup left much to be desired. I ran out of elevation adjustment and could not get the dot zeroed correctly, the added height also made for a hard time finding the dot. At the end of the class, I sent the red dot along with one of the instructors/gunsmiths who milled out a slide for the optic. My natural tendency to aim high with Glocks and lack of any iron sights on the slide, made for a slower presentation and I ended up selling off the slide and optic.
Fast forward a few years and the RDS pistol craze was starting to kick off in a big way. Considering the popularity, I decided to give it another shot. I picked up a CORE and a RMR 02. I was not in love with the mounting solution. The adapter plate design while flexible, never seemed like a solid setup. I still carried the gun quite a bit and used it as my primary training gun for about a year or so.
After putting in the training needed, I quickly saw the merits and decided to get a quality rig by Doug at ATEi. The difference was night and day. The slide is milled to my exact optic, it is much more secure, I have less issues with slight zero wandering from the mount, and the lower height makes it even quicker to pick up the dot.
I now greatly prefer carrying with the dot. On a static square range, it isn't a huge advantage other than longer range shots. However once we start looking at moving targets, it all changes. The ability to actually watch the target instead of my sight is a huge advantage. It also makes shooting in low light quite a bit easier. The only times I have had issues with washing out the dot was when using a 500 lumen U Boat on a paper target at close range. I do not have the same issues with a 3D target in a t shirt.