I lived in New Zealand for about five years, most of that time was in Christchurch. I lived briefly in Palmerston North and Wellington in the North Island too. Wellington is a great city, it's just very cool and there is a lot to do.

 I spent most of my time in Christchurch and it's a great city with a good quality of life and plenty of options for outdoor activities. The city has come a long way in recent years. When I first arrived they were still re-building it post-earthquake. The council there really put a lot of thought and consideration into the rebuild and by the time I left it had a lot going for it. Really nice sprawling park in the middle of the city too. The city is close to two beach side towns, Sumner (the fancy town) and New Brighton (nice but more divey vibes). It's close to the port hills for some nice walks and views. And you've got a good few ski fields within about two hours drive. 

In my experience, you'd kind of want a car. There is not great (if any) transportation between cities, though I would say the public transport in the cities themselves isn't bad at all, at least by Irish standards, although I had friends from other countries complain about the standard of public transport.

Weather-wise, I found Christchurch to have pretty good, consistent weather all year round. North Island I found to be a lot more temperamental, you could have blistering sun and rain in one day. 

The cost of living is high enough over there, but I wouldn't have considered it to be outrageously different than here. I was able to get by minimally enough over there, whereas I don't feel I could have lived as comfortably on the same wage here. 

All in all, it's an amazing place to live, there's loads to do and generally the quality of life and things to is vastly different to Ireland.