Hi irwin8417
Intweresting issue.
There is of course no guarantee that your upgrade to F will clear, or that the flight will move to 2 class and you are lucky enough to score an F seat for a J fare.
Certainly F on the 747 is just fine - same seats as BA First but in a different layout. Still fairly narrow but full flat. And F service is still F service.
I've flown both CX and QF J and my preference is for a full lie flat seat anytime (I'll say it again... if sloping seats were the best way to sleep we'd all saw off the end two legs on our bed at home!).
Service can be equally slow on both QF and CX, but I think CX loses out on the quality of some of the food (their brewed coffee is pretty bland, their cheeses are so-so, some of their mains all taste the same after a while). CX is also fairly mean on the size of their drinks and unless you're drinking wine they mix the weakest alcoholic drinks ever
But CX does win on their inflight entertainment - nice big screen right in front of you (not miles away on the back of the seat in front andd too low to see comfortably).
ok, rant about CX and QF now finished
In summary - QF 747 F is just fine. But no guarantees of the upgrade until 24 hours before departure. If at all.
Choice between CX or QF J... well... flat bed wins for me - even though on my last few trips I have missed out on the double miles as a QF plat - just not worth having to climb up a sloping J bed for 8 hours.
Regards
lme ff