You spend a lot of time in the air hunting and tracking, they have the easiest time locating prey which generally leads to more opportunities to get kills.
But reasons why air first
1.) less mana to stay in form. It really impacts how long you need before dropping down to regain mana.
2.) spirit of the thunder hawk greater enliven let’s you regain moves in the air and further reduces mana cost of staying in form, so more time in air.
3.) I am not sure if it was because of major or I just was sloppy about keeping up passdoor but some final forms can’t always flyto indoor areas
And lastly for power ranking some of the third tier air forms make passable tanks for ranking groups. All but the giant wasp make fine tanks for final forms, excellent dodge plus 20+ dex isn’t too shabby.