Langham in AKL was named best hotel in NZ in 2013, fwiw. Pricing is often lower than the Hilton or Sofitel and it is a nicer hotel.

For SYD there are dozens of good hotel choices, pricing/value varies a lot by date. Westin is a good solid choice and my personal favourite is an apartment hotel on Crown St but that isn't central. SYD hotel prices are high at the best of times, and sky high for special events (due to very high occupancy rates).