I flew Qantas premium economy last year to Australia and UA can't compete with it with Economy Plus. Qantas actually knocks out seats in each row and has extra legroom and a footrest. Add on their on-demand entertainment system, versus the upgrade lottery at UA, and I think you'd need to seriously look at the Qantas flight. Consider also that your EXP status gets you first class lounge access which should also make it more tolerable, particularly if you fly home from Sydney and have table service at the restaurant in the F lounge.

Tom in the Qantas Perth lounge