What I like about AH:
Plane models handle very much like in real life compared to most other sims IMO,
There are lots of Historical/strategic things in ah, Combat Theater, Scenarios Tour Of Duty. (I havent tried TOD or any scenarios yet cuz I don't have an account for MA but they sound very nice),
Terrain Editor that lets you create your own maps, I've allways liked making maps/Scenarios for games.,
A VERY large selection of planes, and more being added every month or so, sometime this month patch 1.10 will be out and we get 9-10 new planes!,
Very good Customer Service.
And if you ever drop in the H2H (H2H is free, its basically multiplayer with up to 8 ppl) I usuelly host historical maps I make with realistic setups and night/day.