I can't really recommend any of the Sydney stores because of the snobbish SAs in all three stores. One exception is when I discovered this SA in Bondi Junction but their stock levels seems the least from the other two.
Are you thinking of purchasing or just for the visit? If you are coming from US, it will be cheaper to buy there than in Sydney. Even as a tourist, you will be entitled to a 9% GST refund which in a way does bring the price down in comparison however I found it still not competitive enough to compare with say US, Europe, HK or Singapore.