I loved them both (and while I was able to talk to Foxy, we didn't get to meet up).
Sydney is THE classic place to see, and you should take the tour of the Opera House (even if you don't see any production there). Melbourne is more "homey", but we loved it as well. If you go there, you can take the Great Ocean Road trip. We did about half of it, as far as the 12 Apostles.