Agreed AA makes the most sense and rewards premium cabin travel. You just need to make sure you fly the 4 AA segments to maintain status. You get access to the Qantas first lounge at LAX which is nicer than what you would get in other programs where you would get business access.
yes the downside is you are lower down in the priority list for an opup upgrade, but it is by no means guaranteed but premium economy to business is one of the easier ones given the size of small size of the premium economy cabin. I much rather have a systemwides that will get you into business if there is an empty seat vs hoping that premium economy is oversold.
Also worth comparing the miles you would earn under each plan.
Looking forward once AA introduces premium economy on to its planes it may make sense to take the AA option and put the upgrade in for business. Likely prices out better via Tokyo than HK.