I've sailed out of NY in winter twice. Once on the Dawn & once on the Gem. We've had fantastic weather, smooth sailing & a delightful trip; we've also been tossed around like a dingy. You can usually lay out by the 2nd day.
We're flying tto Miami for this year's trip b/c I just don't want to deal with the long trip home -- 2 days at sea -- again.
The carribbean itinerary is great. The Gem is a beautiful ship although her color combinations are a bit loud for my tastes.
When you get back it is nice to walk off the ship, hop in a car service & be home rather than having to deal with airports & more travel that last day.