i only go G2A if it's cheap, that is, if i can pull a heavy assault with lock-on launcher or if there is a phalanx aspis turret around. their main advantage is they dont cost any resources and usually get the job done on the other hand, a skyguard or burster max is a waste of resource most times, in my opinion. you invest a full 350/450 nanites just to be able to scare away enemy aircraft, and after they've left there's nothing to do for you anymore. meanwhile, you expose yourself to enemy ground units who are able to deal with you very efficiently since you have AA weaponry. imo, it's a very bad risk-reward ratio that makes me never pull a skyguard/burster max that said, the most fun and most satisfying AA still is a tank with AP cannon: extremely difficult to kill aircraft with, but when it happens it's the best feeling in the game!