UA is the only non-stop in those three on that route. E+ would do it for me, even with the shoddy 747 communal screens (do a search and you'll find the 777 is headed to this route).

QF & NZ are both better in Y due to tv's/service/food. If the extra stop doesn't bother you, SFO-LAX-SYD can get you on the A380 on QF which has a snack bar for Y; while SFO-AKL-SYD on NZ would also work. If earning points/miles is important to you, UA > QF/NZ.

If work will pay for the hotel, also consider a stopover in HNL to break the trip up, with Jetstar or Hawaiian as the second leg.