I tell folk that the NYC technology scene is larger than every Australian technology scene combined. The Bay Area's tech scene is large than every Australian scene multiplied. It is a stark difference.
In Darwin, I could get a job but not, as my father said, a career. In Perth I could get a career, but it would be in moving from backoffice to backoffice, with a lot of pleading for the job in-between. "Why yes, I have 152 years experience in .NET 72.8.1"
Having lived and worked in NYC for a few years, I am pestered by recruiters. Every week I will get one or two emails pitching startups and giants. There is fierce competition for talent -- it's the same position tradies were in during the height of the mining boom.
And I like it here. I am not a beach person, I can buy wine, it's a cultural capital and so on and so forth. I love Darwin, I miss it, but it was never going to be a big enough canvas. I miss my family in Perth but again, not enough of a canvas.
If NYC isn't enough, you are rapidly running out of places to go.