I travel back and forth between Malaysia and Australia every couple of months and I normally fly with Qantas Airways, because they are relatively cheaper than all the other flights. The only problem is that Qantas does not fly into Malaysia, thus, I have to end up transitting in Singapore.
As I said before, Qantas is relatively cheaper as compared to other flights like Singapore Airlines and Malaysia Airlines; however, quality wise, Qantas is not as good.
I once got a return ticket between Singapore and Adelaide for only slightly over A$650, where as Malaysia Airlines and Singapore Airlines would have costs at least A$1200.
With in-flight service wise, we get two meals in the 6 hrs 50 mins flight, with desserts like fruits and juices in between. Plus, they have "New Release" for the in-flight entertainment as well which Malaysia Airlines doesn't have.
The only problem I have is the air crew can be a bit forgetful, and relatively slower when it comes to service. But nonetheless, for such a good deal, I think Qantas is the cheapest option to go.