Definitely prefer the Skybed over the CX J.

I think it is a long enough flight that seat comfort is #1.

That said AVOD on CX is among the best out there. So also depends on whether you plan to sleep or not.

I just flew QF/CX and BA on a Circle pacific and least liked the BA J seat- too narrow and you feel the need to use the privacy screen on BA which just make your space seem even smaller.
AVOD on CX the best- QF and BA about similar