LeeAnne, you didn't mention if you've ever been to NZ before?? If you haven't, I would definitely opt for the Mariner with a couple of days in Auckland and the port stop in Bay of Islands. NZ is amazing! You will still get to see the FP islands this way, even if you do forgo the Motu day. To me it's the best of both worlds. The 6 sea days may or may not appeal to you. I was concerned about having this many sea days when we went to Auckland (reverse itinerary)but it worked out just fine for me. That's something only you can decide. As for ships, there is no comparison.