Determining what/which is MA compliant is the kicker... how does one do that nowadays?
During the 94 AWB manufacturers submitted examples to the BATF (legal or tech branch... I forget which, probably both), for testing, evaluation and ruling in order to determine it's legality.
The BATF would give it's seal of approval and the manufacturers would state in their ads that it was "BATF approved".
Ever since the fed ban expired, it's rare (if ever), that manufacturers even bother with the approval process anymore.
With that in mind, the wisest approach would be to go with an example that was produced during the ban, still available and unchanged during that time.
Which is best? I have no idea.
Personally speaking... I think it's more of a matter of aesthetics than function (at least for SHTF, plinking and fun and games). The light recoil and muzzle climb of an unbraked AR isn't that much different than a braked one.
And not that I'm anal about these kind of things (I'm not... but I can't say the same for the MA AG), a brake could be legal so as not to be a flash suppressor, but if the outer diameter is not within certain specs (I believe it had to be larger than 22mm-23mm), it could also qualify as a grenade launcher