My first key question is what the Qantas programme will deliver to you. Do you intend to go to OZ frequently? You seem to be UK-based now.
I believe TP accrual is easier with BA, leading to OW status, but happy to be corrected on that. But if you’re looking at flying arounf Europe, BA seems to be a more useful programme.
And if in UK, don’t forget the Avios-earnings associated with the (free) BA Amex card. Benefit depends on your annual spend, of course.