I was pleasantly surprised with Carnival. I think that there are so many other variables that are as important as the line itself: itinerary, price, departure port (I am about to spend a week with a bunch of New Yorkers, don't think I'm not thinking about that...), who you are traveling with, etc. Going with the kids? CCL, although my kids were a little turned off by the decor of the Elation. Just a little. It's just like any land based destination- if it was just you and your wife, would you be going to Disneyworld? If you were taking your mother in law, would you be kayaking in the Mekong Delta or working on your tan in Mykonos? If you are taking the kids AND your mother in law, are you going to be booking a Seabourne cruise for 7? If you are in your right mind, are you going to book a cruise filled with New Yorkers and New Jerseyites? I think not.
Anyway, CCL is fine. NCL is fine. Either way the desserts are tasteless and gelatin based, the drinks are outrageous, you will lose in the casino, and you will have the time of your life.