Which one has a better rate, US$ or NZ$?

I'll fly from Auckland to Vanuatu. I want to bring only New Zealand dollar. Can I change New Zealand dollar into the local currency in Vanuatu? Which one has a better rate, US$ or NZ$?

The local currency is neither NZD nor USD

Explain what you mean by "Which one has a better rate?' - obviously with the USD worth more than the NZD you will get more Vanuatu Vatu

92 Vatu = USD$1
73.7 Vatu=NZD$1

Your profile indicates you are Australian. Australian dollars will give you the best rate. It is not worth changing what you already have, and then changing again to Vatu, as you will be paying fees etc.