It's a pretty hard decision. I'm Mongolian myself so the cold weather and snow in Europe is appealing, and Berlin summers are to die for. Melbourne is just kinda boring in some ways, very little historical sites (and most of these being irrelevant to me), being far away from everything.
Its true that getting residency in Australia seems better as a long-term thing (lived here for a while as a kid as well, plus the whole immigrant nation thing), plus English isn't even a foreign language to me. On the other hand, living in Berlin for a while while young is very appealing as a travel nut, and who knows, I might decide to settle down there as well, since last time I was there I pretty damn happy, though I realise that I'd always be a foreigner in Germany, as opposed to in Australia.