Being listed in Google?

[James]

run what ever works best for you Lemon, by all means do not take my advice.

It is your choice if you want to have 2 versions of your website indexed in non www and www versions.

 

[Lemon]

But google hasn't indexed my site twice I get the same results for site:domain.com.au and site:www.domain.com.au. I'm not sure I see the point in generating different content for the same results.

 

[James]

I think if you refer back to the original Case here the user had 4 different versions of domains indexed.

For your website a different case,
If have a preferred domain set in Webmaster tools then it will use that, if you have non www and www redirect it works better for SEO becuase all non www links will be 301ed to your www version site.

The list of benefit goes on.