Fir me, if the timing suited my availability, I would take Dave's suggestion of QF32. I really dislike the short overnight hop from Asia (SIN/BKK/HKG) to SYD as its not long enough to get a decent sleep, so taking that as a daytime flight would be my choice.
I have a slight preference for the QF seat over the BA seat, but its not as significant as the choice of a daytime flight.
Oh yes, most impostantly, BA has better scotch.