Wholly apart from the relative quality of AA Business vs. FJ Business, I would choose the SYD routing because of the greater options there in the event of IROPS.
I would only consider the SYD-LAX F option if you can book MEL-SYD with miles -- and have AA put both awards on a single PNR -- so that you would be protected in the event of IROPS on the MEL-SYD leg.