Unless there is a glaring reason to move to another FFP I believe you are generally better off staying with the local program - simply because you will probably be needing the "elite leverage" on domestic flights in the future, or extra help solving an urgent situation.

If you spend most of your time in Australia then QF might be the way to go, especially since you may end up with a free Qantas Club membership when reaching oneworld Emerald. From my experience, Qantas doesn't give AA EXP members any benefits in the area of comp upgrades, etc. so you wouldn't benefit that much from AA PLT. Don't know about the BA program, but it is probably similar to QF.