I pretty much only fly in Y. Unless hubby (who is Plat with VA) decides to upgrade me himself, or I use a whole year's worth of credit card points for a J flight to PER with QF, so I think I'm qualified to comment here.
I do not enjoy flying Y on VA because they are almost exclusively 737s, particularly up the east coast, and I am fat (not "spill over the seat" fat, but "only just fit" fat, which is still uncomfortable in a 737). At least with QF, if you pick your flight carefully, you can get an A330 MEL-SYD. Even PER-MEL the red eye flight is always a 737 on VA, which suggests that one or more of the day MEL-PER flights must be as well (probably, I've never checked this). Putting 200 pax on the red-eye in a 737 may be a good scheduling decision because it puts the plane in MEL for the first morning flight, but it's tantamount to torture as far as I am concerned (hubby has made that mistake once, despite me warning him against it, he thought it would be okay if he was in J. It wasn't.). I only fly JQ if I can't avoid it. My overarching memory of the flights I have taken with JQ is of my knees squished up against the seat in front and I'm only 168cm tall. I've not found leg room to be a major issue on QF or JQ.
(Hubby is often finding his VA MEL-PER and return J flights downgraded from A330 to 737 BTW, but I digress)
So there's that reason not to fly VA, all things being equal. The food I think is less of an issue for me, but perhaps that's because my last fight SYD-MEL on QF, the boxed dinner was so bad I only ate a few morsels of it before giving up. And salt did not help. AND they tried to charge me for wine with their dinner service (I was not aware that anything had changed), but when I looked perplexed he relented and just gave it to me. It was an A330 for reasons above, so the seat was relatively spacious and comfortable, though perhaps a little hard. My last flight with VA was BNE-MEL on a 737 and we had to buy our food from the menu IIRC. Which was fine as at least what you buy is decent quality for what it is. (I do love the Moreish nuts/pretzel packs on VA).
So for me, on balance, I will take the flight where an A330 (Or Embraer) is operated. And yes, I will get pissy if they swap out the aircraft. I always travel with my phone and iPad so IFE for me is take it or leave it stuff. I always get on the plane with an outrageously expensive bottle of diet coke that I've purchased in the terminal because for some reason airlines think DC is the same product as Zero and any DC addict will tell you it is no such thing. So I've already bought a drink, buying a snack seems to be no great stretch, but on QF, I don't even get that option if I don't like the offering. So as I said, the plane itself and the timing of the flight makes the decision for me.
