Number one question for choice of carrier will be: How much do you want a flat flat bed, ie not one that is flat at an angle? CX, QF and SQ all have flat at an angle (and QF is still in the process of fitting them during 2004). BA has the only truly flat bed to Australasia, but it is narrower than other seats and some people don't like the forward-backward arrangement. (Also you'd have to interline onto QF in Sydney or somewhere similar.)
There was an article about this in the New York Times -
http://www.nytimes.com/2004/01/27/business/27sleep.html - may require free registration to read.
As far as route is concerned, do you want to do anything at a stop on the way or do you just want to get there? If you just want to get there, route is only important for overall length of journey.