I find the angled fore grip more comfortable to shoot from. Especially since I have large hands, and do the "thumb over barrel" driving forward method that magpul likes to show.
But with vertical grips its easier to take weight off of your primary hand when not shooting (like while patrolling). And you have the advantage of using it as a monopod, or "push/pulling" it on cover or barricades for a more stable shot. Also, retention is much better if someone is trying to wrangle it from your hands or you need to muzzle thump someone.
But since I'm not patrolling, actively shooting behind cover, or getting it melee fights with it... I use the AFG. When I do use a vert fore grip, I prefer stubby or shorter grips, otherwise I feel like I'm getting caught up on my sling.
It bugs me seeing guys "broomhandle" their vert grips. But then again, it bugs me seeing guys grip their magwell too. Just rock whatever works for you.