I just did a little back-of-the-envelope comparison of the benefits of this SAMPLE route: CAI-LHR-FCO-LHR-DFW-YVR-JFK-ORD-SLC-LAX-SYD-NOU-SYD-HKG-BKK-LHR-DXB using the AA v. the QF FF program, and assuming you challenge up to Platinum with AA before the start.

Bottom line, you'd earn roughly 87,741 redeemable miles with AA and have Platinum status (Oneworld Sapphire) whereas you'd earn around 68,200 points with Qantas and have Platinum (Oneworld Emerald) status with QFF, i.e. 1500+ status credits and 4 Qantas-metal sectors. (Note I am not an expert on the QFF, so I could be quite wrong.)

So I'd look at both airlines' redemption charts and decide if staying with QFF vs. "defecting" to AAdvantage makes any sense. AA is getting rid of its "soft landing" feature (you only fall one level regardless of how little flying you do) so if you didn't keep up flying 50,000 or more miles annually it would be a one-time thing; of course you won't keep Qantas status indefinitely either.

One note on the previous posts - VIE-PAR is operated by Nikki, which is not included in my copy of the OWE rules as an eligible carrier. Maybe something's changed?