I recently made the switch from VA Gold to QF, but I think my reasons were a little more... fickle, I suppose, in some eyes.
a) I only ever got VA Gold because I could pool SCs from my partner, so I definitely won't be able to get it on QF in my own right which has a higher threshold to hit and maintain. If family pooling is important to you, keep that in mind that it's not quite the same with QF.
b) I switched because I also liked that QF fly their own metal to virtually everywhere I would want to go, and where they don't, I like the OW network airlines that do.
c) Qantas Club virtually gave me all the benefits I'd be looking for, though there are a couple of nice Gold benefits (priority boarding, baggage etc) that I'll miss.
d) Rightly or wrongly, I feel like VA's network/frequent flyer program is always changing and it was getting frustrating. eg. trying to figure out which VA-partner lounge you can access when, depending on where you're flying, who you are, the moon phase, current financial situation in Ghana etc...
e) Almost everyone in my company flies QF, and I was getting sick of "not wanting to inconvenience them" so always got earlier flights outbound and later flights inbound which was impacting my own work/life balance.
f) Lifetime recognition, though I may never actually hit LTS, is still a nice ambition and I like that it's offered (though regrets for the last 4 years of not building that total...).
g) My bank offers a credit card that earns QF points and works with Apple Pay, but doesn't have a card that earns VA points.
h) I'm a real sucker for the Australiana that QF plays up so well
. Also recently when work flew me QF when I wanted VA/NZ (pre-switch), I was thoroughly impressed with the professionalism, quality, service of the crew and then the safety video showing places from around Australia really made me feel like I was 'going home'. It's soft, it's a bit of a toss, but I found it a really nice touch and it spoke to me.
Certainly not the biggest reasons in the world to jump ship, but they're a few of the things that I took into consideration