Thanks guys for your responses, I read them all with great interest.
Why Premium ? Well its just that the cabin doesnt have as many people and I would personally feel better.
I would have loved to try the A380 but recent events (AvHerald) concern me. My rationale is that the 747, though older is well proven and the pilots know it so well and maybe a lot of the bugs have been ironed out.
Last year I flew Syd to Melb on the way down, a very cramped 737-400, which reminded me of a bus inside. I hated that flight.
On the return, I flew to Syd with a Qantas A330-200, with a configuration of 2-4-2. My daughter and I sat in the two seats near the window. A bigger plane and much better (for me relaxed) flight. Dont know if I could stay there for 12 hours but the 90 minute flight was good.