Originally Posted by
berlinflyer83
You could earn status miles on AA even when flying BA. And if you do the challenge, you'd get AA PLT after your first trip in J, which gives you priority boarding on BA. You'd already have lounge access with AA PLT, but you would get that from the J ticket too
Also, since airberlin is joining, you might keep your AA PLT status for all the OW benefits, and then earn against topbonus later. Hopefully the benefits get better once they join. I hope the program will be more extensive.
FS_FRA would have lounge access everywhere except in the US for domestic flights if he were to stick with AA. Also, to complete the challenge they would have to fly on AA metal. If the TATL flights are in J, I would say go with BA. Flights in higher classes earn many tier points, you get lounge access domestically with AA (though this might be moot if only flying business TATL and not taking any domestic flights); BA have published they have a soft-landing policy whereas AA can decide to do away with it.
BA are not as generous with upgrades, plus redemptions are cheaper with AA. If that's important then go with AA.
I don't know much about airberlin's programme but they might be worth considering once they join
oneworld.