It depends on the travel patterns and how you an obtain status.

I actually am Ba Silver first - main reason lounge access even on AA flights - and now am AA Gold, will go for Plat by challenge on the next flight (due to the duration of Platinum I decided not to go for Plat on the Gold challenge).

I will keep BA Silver but try to look at how to obtain it cost effective. Having both BA and AA allows me some benefits when flying with either of them and having the difference of BA / AA on the crossing of the atlantic there is even more reason to keep both.

With EXP you could think about retrieving more miles for the million mark, if you are satisfied with normal lounges in america / canada you for example do not need to retain emerald but a mere saphire is enough for lounge access on AA.