Different strokes for different folks. Sometimes I use one, sometimes I don't. If I had to equip all of my rifles the same way, I'd leave foregrips off of them.
For a while the full-sized VFG was all the rage, then the stubby, now the AFG. The memo is going around that anyone not using the arm-out/Magpul AFG combo is way, way behind the times.
Personally, I say try them all and find what works for you. I prefer adaptability, since sometimes you may be behind cover, prone, on your side, whatever. The arm-out technique is great for muzzle control, but muzzle control is not the only consideration when moving with and shooting a rifle, especially from unconventional and uncomfortable position. I believe that many instructors, both of rifles and pistols, put far too much emphasis on assuming the proper stance/grip. It seems to me that the exigencies of life-or-death situations may often prohibit you from shooting in the optimal position.
I've never "been there or done that," never been shot at, so take my opinion for what it's worth.