which is harder..air combat or GVing in game?
Hands down air combat.
You can take everything that the gv aspect has in the game, and apply it to the air. Distance shooting, not missing your shot or your dead, getting jumped (snuck up on), and whatever else you can think of. Then you add the 3d aspect, the many different offensive and defensive maneuvers and at what air speed you can execute them, knowing when and if you should deploy flaps, trimming your plane, closure rates, that it all happens faster, and so on, and so on.
Given an even learning time line it takes much longer to become really good at air combat, just because there is more to learn.
I prefer air combat, but i have fun tanking from time to time, and like to defend bases in wirbles and ostis.