I spent quite some time researching the FFHG's that are highly praised on ARFCOM and they all have their little quirks like fitment issues, how it attaches to the barrel nut, how it can spin, etc... I haven't seen a totally bulletproof design that I liked.
Samson and Troy: Adds a decent amount of weight (manageable), but relies on two wings that clamp against the upper receiver. Quality of fit / play will depend on upper receiver design. It just seems that with enough vibration the aluminum can wear away by a few thousandths and result in loose HGs?
Midwest: It's one heavy SOB and based on Forest's sheet, it's heavier than the ARMS SIR.
Daniel Defense: Other than a lock ring, there's no way to secure the HG to the barrel nut other than the SS pins. It's light though.
LaRue 7.0: Good design but it is out of stock for several weeks+. With the rail covers, it will still add about 1/2 to 3/4 of a pound to the front end (for a quarter of a grand).
YHM FF tubes: I have one for my 24" AR-15 (Harris bipod, mostly a bench/prone/target shooter) and the overall setup weighs 11lb w/o a magazine. The HG can get loose and spin around, so I made sure to tighten the lock ring and to use threadlocker. I don't like this concept for a battle carbine. I don't want stuff coming loose in my hand during a course.
If I were deciding which to approve for military issue, none of these would be approved except for maybe the LaRue.