Remember that if you have BAEC you should also have IB+ since avios as you can easily transfer between the two. IB tends to give status easier and BA seems to be better on the avios, so which one you use to fly with would depend on that. Granted, the differences are relatively minor.

I have no status (working on it) but I generally stick with IB since I'll be at MAD long term. My experience with their customer service has generally been good, but I definitely know English can be an issue if you don't Spanish.