I would actually agree that the AA seats are better than the "old" BA seats, however not so much so that it would actually be worth dealing with the rest of AA's product offering (food, service, etc.).
With the possibility of getting the new BA seat, hands down the answer is BA. It is no question, unless you are more concerned with mileage earning, in which case you'll have to fly AA if you are trying to earn AA miles and vice versa.