Frank...I've been to Australia, but never by ship. And have yet to visit New Zealand. I can't wait to get your input. For example, I've heard NZ is one of the most beautiful places on earth, but does a visit by ship do it justice? Is there enough time spent there to see the spectacular beauty? I can't wait to get your feedback to the question above.
I'd probably opt for Orient's Marcho Polo, although several ships (including Renaissance) are having extensive seasons in this area.