Welcome to FlyerTalk TallGuyUtah,

Firstly, when redeeming BA miles for economy flights, it is highly unlikely you will then be able to pay for an upgrade.

As for comparing QF to CX, IMHO there's not much between them in economy, and a lot of it comes down to personal taste and preference.

Personally, I'd rate CX ahead of QF for cabin comfort. I'm 6'1" and I find CX's new shell seat surprisingly comfortable. CX operate A330s between HKG/SYD, which are newer, clean and it's a fairly quiet cabin. QF operate both A330s and B747s. Neither have particularly generous seat pitch, around 31" for QF and 32" for CX.

Both have very good entertainment on this route, but I'd rate QF ahead slightly as their selection caters to a broader range of tastes.

I'd also rate QF's catering ahead of CX, but again only marginally. Some years back I'd have tipped the scales in CX's favour, but whilst all airlines have cut back on catering, I still think QF does a fine job in economy.

The only other factor for me is service delivery. All airlines have good and not so good crews, but in many years of flying both CX and QF, I'd have to say CX delivers a more consistent level of service. It's not to say it's robotic, just more consistent. I think culturally, QF crews may have a greater level of autonomy, which can reflect in the service (both positively and negatively).

I hope this helps, you're pretty safe either way, have a great trip.