Ive used the surefire rail and the YHM.
The YHM is on my rifle. They arent coming off either. I like the ability to put a sling stud into the hanguard rather than having to buy an adapter to put on the rail. Uses much less space. Mine are ROCK solid. No movement in any direction. All my gear slides on and off the rails easily. Id buy another set. The only negative I can think of is no heat guards. I dont fire full auto, so I really dont care. Ive dumped a few mags quick and it hasnt bothered me.
My buddy has the surefire rail on his. Hes had it on there for over a year of hard use, and its held up well. It fits tight, and all the rails are in spec. Has heat shields for those that care. His is a little lighter than mine. Not noticably when the rifles are geared equally.
Personally, I wouldnt hesitate to buy the surefire rail at all. Matter of fact, I planned to if the YHM's didnt meet my standards. Since they did..........