Regarding the waters in and out of NYC:
This really depends on how choppy the water is on the days you sail. When we sailed out of NYC on June 29th, the waters were calm all the way to Bermuda. But when we left Bermuda on July 4th, the water was choppy and that night and all the next day at sea, you could definitely feel the ship rolling and pitching, but I don't think it made many, if any, of the passengers or crew sick. The captain said we had hit 15' waves overnight on Friday into Saturday. On Saturday even though the weather was nice, they had the pool closed because the waves in the pool had been sloshing all over the deck. Later in the day they reopened it though.
Regarding pricing: I've done a lot of research and realize that Disney cruises are more expensive, cabin type for cabin type, than most of the other cruise lines. But after looking into the teen's program (our DSs will both be teens when we sail next summer), we feel it's worth it. Also the Disne ships are beautiful, and while the RCI ships are beautiful too, there's just no comparing the attention to the detail that Disney provides such as the themed restaurants, themed lounges, etc.
Regarding food: I can't make a comparison since I haven't been on a
Disney cruise yet. The food on RCI's Nordic Empress was good. Some dishes were outstanding while some were just "fine".
We're doing the Disney cruise next year because our DSs will be with us and we love everything we've been reading about Disney cruise lines, but we're going to book RCI's 9-night Voyager out of NYC for the following year when it'll be just the adults going because we wouldn't need to fly, and we like the itinerary and the fact that it's a 9 night sailing.