I think both F classes overall are excellent. In my last experience, however, I did feel that QF slightly edged out CX.

Firstly, the meals on QF were absolutely fantastic. They were comparable to a decent restaurant in terms of taste and food quality and I am not much for airline food. While food on CX was also good, QF, in my experience, was far better.

I also think I got lucky in terms of crew. The crew on my flight (DXB-SYD) were fantastic.

That said both are great options and you can't go wrong either way.

The only thing I'll add is that if you are not a OW freq flyer, then QF F gives you access to their amazing F class lounge in Sydney. Something else to keep in mind.