I would vote for AA also. We use Logan for domestic (earning miles) and international (spending them). Although using London as a gateway to Europe and beyond can be problematic since TATL award travel is not available on BA, we have found Iberia (using Madrid as a gateway city) to be much more readily available in terms of business class awards. Not sure of the effect of the AA/BA/IB consolidation that is looming will have upon award travel.

My wife and I are lifetime gold and plt status, respectively, and it was the purchases, dining, credit cards, and other promotions mentioned in the prior post that got us there.