Thanks for the info. I think I'll go with the 1 night version. Looking more closely at the itinerary, you spend most of the 2nd day kayaking on the 2 night trip. I'd probably enjoy that, but I don't think everyone else would!
This boat sounds nicer than the Emeraude, if only because it holds ~50% less people. Looking at the schedules for both, you get ~1-1.5 hrs more time on the bay on this boat, presumably because it takes less time to disembark.
Try either the Huong Hai and Dragon Pearl Junk cruises. You can book Huong Hai private for $450.00 per night. Food is not buffet-cooked fresh, although not off a menu. We spent 2 nights just sailing around-no kayaking for us. Time at the cave, a couple of beaches, looking at all the floating villages and just enjoying the scenery. Fantastic experience.