well theres no flights direct MEL-AYQ so either way your connecting via sydney on that one really

The main difference domestically between DJ (Virgin Aus) and QF is the fact that QF includes food & Drink of some kind in the cost of the basic fare.

If you book a saver fare with DJ your paying for your food/bev onboard. Flexi's with DJ include a present meal/drink similar to QF.

In regards to the business fares i havent flown DJ business but the product themselves are extremely close related. so much of a muchness.

its like comparing AA and UA. Essentially the same just slight differences.