If the choice was between a QF 747 and a QF A330, it would depend on what class I was getting. I'd likely go with the 747 because of the upper deck side bins and the Premium Economy cabin.
The only thing the A330 has going for it vs the 747 is the better Business class seats.
Though, while I would hope things here and in Japan are resolved enough that both have reopened to an extent that allows for flights to return to something resembling normal and for Australians to actually enter Japan (Japan has blocked visa waver nations and suspended visas as of April 3rd with no end known end date), it is unlikely that QF will be using 747s.
Given the effects of the current pandemic, and the known fleet plans Qantas has, there is low chance that any of the QF 747s will fly in revenue passenger service again.
I'd be looking at the option for a Qantas flight between Australia and Tokyo as being between a 787 or A330.