Auckland is another big city. It does have some interesting sites and is lovely. But Napier is an experience. We were only there for a few hours and really wished we could have stayed longer. The history and explanation of the earthquakes that caused the rebuilding in the art deco style is unique to Napier. The locals put on a great welcome for the Tour ships. We did a Viator tour.
Just a heads up. We booked a private tour in Akaroa, to spend the day with the local mail delivery and tour the Eastern Bays. This tour has great reviews and we were really looking forward to it. However, because of rough seas the harbour was closed and we sailed on by. NO REFUND because we didn't give them 24 hours notice. The tour operator said we should claim through our trip insurance but we now know that you need a special rider for "event cancellation" in order to claim such a loss.