Generally, BA bookings will involve a BA codeshare, which will book into I class with a BA flight number.

As such, you will earn more TPs on the domestic leg, but potentially slightly fewer Avios on the international business leg, and at the risk that your status, etc. won't propagate properly into the BA part of the booking on the BA PNR.

So if 70 TPs matter, and/or the extra avios from the domestic flight outweigh the slight loss on the international portion, and provided you don't want to upgrade an I-class flight using Avios into First, book AA. (As a GGL you won't need to worry about qualifying flights, but that could be a concern for someone TP running their way to silver but mainly flying on redemptions or non-BA flights).