My only experience in Sydney (other than way back in 1971) was three years ago at the Marriott at Circular Quay which was excellent. Stayed there a couple of nights before embarking on an RCL cruise and the location was so convenient to the ship that we simply walked with all our luggage from the hotel to the ship.

The room was very nice and the lounge (which may have changed since then) was great fro breakfast and evening snacks. I wouldn't hesitate to go back there.