I have the green rail master on my Ruger Mk IV tactical and it has been great for eliminating varmints at night especially when used in conjunction with a flash light. I had previously used a red dot sight for this application and it worked but the green laser worked better. As for the 19x, I had the green laser grip on that which added some bulk to the grip area but I didn't find the added size to be a problem in this area. I prefer the railmaster's location but that would prevent me from using my favorite leather holster and would force me to look for some kind of custom kydex holster and I don't want to do that.
You're right about all the advantages of the laser that you just mentioned. The ability to shoot from non-standard shooting positions such as one might potentially encounter in a combat situation is a big bonus. Remember the scene from the Dirty Dozen where Lee Marvin and Charles Bronson
stroll up to the car full of Nazis in the middle of the night and then rapidly dispatch them all with a suppressed period incorrect Beretta Jetfire .25 acp? How handy would a laser have been in that situation? Another thing that's nice about them is they let you see how bad or how good your shooting fundamentals really are during dry fire practice. If you can you see that dot shaking and moving all around on the target when you squeeze the trigger, it's a pretty good indicator of where your accuracy problems lie. And like I said, they make head shots a breeze which would be useful if you found yourself up against a bad guy with body armor which is an increasingly likely threat. Given all the advantages that a laser confers, I don't know if a red dot sight would actually be superior; although, I'm sure it's a good tool for many applications. I think they're both great tools that one should become comfortable with using.