I came across this post while trying to plan my first trip to Sydney, so I don't have input on which hotels are better but wanted to add that Four Seasons, Park Hyatt, and Langham (as well as Shangri-La) are all part of AMEX FHR, so if you are able to book through that program you might consider it. Langham offers a $100 spa credit
, but the others all offer $100 food & bev credits ^ plus of course free breakfast through FHR.