I know many people who've got to NZ have said 'If you've got it, ship it because stuff can be very expensive to replace there' but, if you haven't got that much to begin with, the cost of shipping might be more than your belongings would cost to replace.
A shared container or even having your things palleted up would be cheaper than a sole-user container. I think a chat with a couple of shippers might be helpful so you can ask their advice and get some form of costing for the different methods available to you. Get a few quotes so you can compare prices and services. There's a list of shippers on the
NZ Website List .