Good question! We're heading to Hamilton because I have family there (I'm a Kiwi) & we have job opportunities for OH.
Interesting what you said about Christchurch. I grew up there & considered moving back there this time, one reason being the weather! You say its cold, yes in the winter it is, but its usually crisp, cold & sunny. For me, beats the rain & fog you can get further north, such as in Auckland & Hamilton. Also, the summer is dry as opposed to the humidity of Auckland.
My 2 cents worth & its probably all change now cos of global warming
Sal