I think I'd go both.....
I've been back and forth all days moving my stuff from house to house.
I've passed the Harbour Bridge and Opera House about 3 times today, and I'm sure it only cost $5 in fuel
But seriously, if you're coming down to Australia..... it's a very big place and so far from Europe. You have to do it seriously. Some spotting, some sightseeing.
Area wise, it's roughly the same size as mainland USA or continental Europe.
A short drive here is a 3 hour drive from Sydney to Canberra. A flight from Sydney to Perth (East to West) is around 5 hours. A flight from Hobart to Darwin (South to North) is over 5 hours.
As I've said before, I can help anyone with both.
Expect prices for hotels and food to be cheaper than Europe, but the Australian dollar is getting quite strong against the USD (not sure of effect against Euro).
Respected users.... If my replies are useful, then by all means...