Catering is a lot tighter in the past 2 years than in the past; QF and CX are not bad for having extra meals, particularly in J (with QF's large J config), while BA often caters exactly 0 extra meals. In fact BA often won't upgrade pax with special meals ordered (lots of airlines have that policy). Not sure about QF, but something to consider if you want upgrades.

The QF menu is pretty cleverly chosen from a dietary restriction standpoint (not just vegetarian). Lots of dishes are orthogonal in their ingredient lists, so it is possible to accomodate lots of different dietary restrictions. Sometimes QF does some clever things (but few people notice). Of the non-Asian airlines QF probably has the best vegetarian offerings on the regular menu (as mentioned seafood is a sure thing, but often there are vegetarian pasta dishes and mushroom dishes too).