I like the A2, personally.
Perhaps more importantly I recently saw this question put to a number of guys that I would consider serious experts in whacking deserving people with AR-type rifles...
Most common response: A2. Cheap, works on the flash fairly well. No excessive muzzle blast for other guys you're shooting with.
Most common reason for differing responses: "mainly shoot with a suppressor".
I agree, mostly.
I've said before that the A2 is very hard to beat for what it offers the shooter; which is some compensation for muzzle climb and decent flash suppression at a cheap price.
I can say that given my skill level, there are things that I can do using a good muzzle brake/comp that I simply can't do with an A2. A good brake does help me shoot faster and more accurately.
Getting back to your points, I think that most of the professional face shooters and top tier trainers out there really like the A2 because of a few reasons:
1) It's not obnoxious to shoot on a course. Shooting next to someone using a brake is generally not a pleasant experience. At the bench I've annoyed many shooters who had to suffer through my muzzle brake testing sessions. But I would never run a brake on a course. Some people are really adverse to muzzle blast and it could ruin their experience.
2) They know how to shoot. Most of the guys I think you are talking about put thousands of rounds a month through their AR's and they know how to mitigate recoil through proper technique. The advantages that a muzzle brake would give them aren't worth the trade off for the constant teeth rattling they would give their students or teammates. The A2 does help to mitigate muzzle climb and that is enough for them.
3) They aren't primarily concerned with competition, where the advantages of a muzzle brake really shines. You see all manner of muzzle devices on three gun rifles and competition guns, because they do work well to improve times and hits. But competition is an individual event where the shooters aren't concerned with what their teammates or students are experiencing.
So...I would say if you are a novice shooter or a competition shooter who wants to shoot fast
and accurately
and you aren't worried about generating a whole lot of noise/blast
and/or you don't have a whole lot of time to train, then invest in a good muzzle brake, it will improve your shooting. Just don't be "that guy" and use one on a course. If you are a decent shooter and participate in a lot of courses, use an A2.
Having said all the above, the DLASK A6 is best muzzle brake I've ever used on both for the VZ and the AR.
And just as info, I just reinstalled an A2 on my AR. I just don't like annoying people.