I would suggest that you choose the state, which has the highest demand for your job. You can use seek.com.au, which is one of the most used job search engines in Australia, to search for your job in each of the major cities. In other words, I suggest following the following steps. 

1. Visit seek.com.au
2. Enter the keywords, which are relevant to your career, e.g. fixing cars or factory maintenance engineer 
3. For the city, enter Sydney 
4. Read the available positions and record the number of positions, which are related to your career

Then, repeat the above steps, but using a different city each time. The number of available positions in your career provides you with a good indication of work availability in that state.