I would say put your miles in QF and use that as your FFP, as you will reach Platinum with those four trips alone. You wouldn't even reach top tier with AA (you'd be at ~77k Q points and would need a few mileage runs to make Executive Platinum). QF Platinum gets you complimentary membership to the Qantas club which also gets you into Admirals Clubs and other lounges. For more info on QF benefits click here.