I've been on the Mariner - to Alaska, and the PG 7 day. The PG is all about French Polynesia - the Mariner sails through FP. That's the real difference. Yes, the Mariner is a nicer ship, with bigger rooms and better food. It doesn't do the motus because it is too big for those lagoons, and missing the motus is missing an experience 'not to be missed'. I'd vote for the pre-cruise trip to New Zealand, which is really a land vacation place, and the full immersion cruise in French Polynesia. That said, you can't make a bad decision!

David