I have found that less is more. First I used a VFG, then I got fancy with a Magpul AFG......Now finally I just have a slick Bravo Company 13" KMR and have found that the lack of a fixed reference point is much better.
On a square range a VFG/AFG/handstop is great.......you're standing there in a perfect fighting position shooting a target....it's easy to reference the same spot on your handguard and its comfortable.
Now get yourself uncomfortable....start shooting prone, supine, under, over, around, or through barricades, vehicles, fences, etc. Sometimes you have to cant the carbine at awkward angle (say 90 degrees). Now its not so easy to get your hand in the position where your VFG/AFG/handstop is and in some cases the VFG/AFG/handstop becomes a liability in that it gets in the way of how and where you need to grab the carbine. They can also become snag hazards around certain obstacles and barricades. Slicker is more betterer
Just my .02. YMMV