Probably UNSW. USYD is better for humanitarian fields whereas UNSW is better for engineering, business, and science related courses. QS states UNSW 44th in the world for natural sciences (includes physics), whereas USYD is tied with some other uni at 58. But ANU is better than both, and if you're willing to go to Canberra that will be the better choice.
Are you planning on going down the route of clinical psychology? Both unis have good programs for clinical psychology post-grad. It would probalbly come down to personal preference.