I am starting a job that will require 4-6 trips per yr SEA-LHR as well as 1 SEA-SYD.

I am Australian so would like to be able to use miles for QF upgrades when traveling with the family (would also like op-up SEA-LHR when possible).

So trying to decide between BA or AA for my ff program. I could get oneworld sapphire status on BA with my itinerary but am curious whether AA is a better option. Also, do either have an advantage in redemption for QF upgrades.

(1) home airport - SEA
(2) miles flown each year & in what class? - 50K in Y
(3) types of fares bought - economy or flex economy
(4) choice of airlines/cabins. work and/or pleasure? - work - BA, AA, QF
(5) routes flown most often - SEA-LHR (4-6 times per year), SEA-SYD (1 per yr)
(6) current FFP status - none
(7) What is most important to you in a FFP? - lounge access, priority services, good redemption rates. (in that order)
(8) Preferred Airlines - QF, BA, AA