Yeah, there is no reason to deal with BA at this point since SPG transfers to AA. As everyone else said, AA charges less miles and you won't pay the fuel surcharge. Save the BA Avios points for short-haul domestic or trip down to South America.

Convert the SPG to AA as soon as possible.

110,000 a person in Business class for AA
70,000 in economy

If you are short some points, you can always fly economy one way and business the other.