To be fair, New Zealand is also the top of the world (1st equal), and Australia has a respectable score. I love the idea of a European Union, but I'd prefer a union of Australia and New Zealand. We've got so much in common.
What benefits would a Australia-New Zealand union provide, beyond the very close cooperation that already seems to occur?
If they were one country, NZ'ers wouldn't be so offended (real or faked) that you called them Australians. :-D
Rugby World Cup domination.
We already have free trade and a joint labour market. This benefits both countries hugely. Any other union would have very questionable benefits (currency, federal government). We should try to extend our free trade zone and labour market. Shortage of cheap labour in New Zealand.