British Expats - Australia vs. New Zealand

[x-posting to the Australia forum as well]

I'm honestly not trying to start a flamewar here! Just looking for opinions on the differences between the two countries.

First off my intro and reason for asking. I'm a 25 yo male, single, do all my work on the internet. I'm kind of starting off my life a perpetual nomad. I'm originally from Vancouver, Canada, but I lived from 2002-2005 in Costa Rica. I'm looking for a place to hang out for about three months in the January-May window and Australia and New Zealand (among other countries) have piqued interest.

I don't know a lot about these two countries, but I'm interested in the opinions of people here what the differences are. Every city has a personality; can you give me an idea of what the personalities in the major cities of these two countries are? I've read a fair bit about the major cities but I'm more interested in a compare and contrast that is hard to find by mere internet searching. Kinds of things like, which city is more busy, which is more laid back? Which cities are more commercialized and developed and which are a little more quiet? What are the differences between the people? That kind of thing.

Thanks for your time!