ANU, Sydney U, Melbourne U 揀邊間好?

Depends on your interest and your budget.

The standard of living in decending order:
Canberra > Sydney > Melbourne.

Are you going back to HK to work? If so and budget is not your concern, I would choose Melbourne Uni as they seldom hv external courses for overseas students as ANU does. I am afraid that the employer may think you obtain ur degree by distance learning, like the school advertised with Li Lai Shan. ha

For Sydney Uni, if you just study Law, it's gd but for media & communication.It seems UNSW is more famous in this subject.

But if you are working in Australia, I can't see any different with any of the degree as they are all accredited uni here.