BA F over QF J any day of the week, especially if:
QF J is on the A380 and the very tired/outdated Skybed II, and
It means getting into either the Mel or Syd QF Flounge. Enormous step up from the J Lounge.
I've flown BA F SYD-LHR on 777 and 747 - probably prefer the 747 over the 777 but very...