The MOS system has some flaws. If you plan on putting the gun through any rigor the MOS system probably will fall short of expectations. Now the benefit of the MOS system is you can try different RDS's and find out which one works for you.thanks for the insight and for starting this thread at the perfect time. Im weighing pros and cons of my next pistol which will have an RDS on it. Orignially my idea was acquire a used G19 in good shape, have the slide milled add suppressor sights and an RMR and go. Then I found the Sig 320 Rx which is more ergonomical but the sight felt cheaper and I had doubts about its durability. Now the 5th gen G19 offers a model with the slide cut from the factory for a RDS (G19 MOS). I think that option might be the way I go seeing as its gonna be within the same ballpark, cost wise, as if I purchased a used Glock built it up from there, but the platform would be brand new as opposed to someones trade in.