I have just been through this exercise myself and it comes down to 2 providers - Telecom & 2 degrees.
They both offer the same bundle deal now. (note the link to the comparison article posted here is Nov 2012 - things have since changed).
I decided on Telecom, as they do have better coverage, despite 2 degrees being talked up a lot on here.
Telecom appear to have lifted their game to match 2 degrees in terms of value bundles, with the added bonus of better coverage outside metro areas.
Call into a Telecom NZ shop when you get there, pay $5 for a local SIM & ph number and then $19 value bundle will get 100mins talk, unlimited txt & 500mb of data - should be plenty for 2 weeks browsing interweb
http://www.telecom.co.nz/mobile/mobile/plansandpricing/prepaid/
Despite this, I just don't get why some still insist on 2 degrees when telecom offers the same deal now but with better coverage...?