It is a personal thing of course, but to my tastes Royal Caribbean's food is not any better than Carnival or NCL serves. I actually find Carnival to have the edge, especially in the main dining room. They have all made cuts in their food costs, as well as having fewer crew members covering more tables and staterooms.
Royal Caribbean has prettier ships, and at least on the larger ships they also have high-end shows. When you can see a true Broadway musical on a ship, as on Oasis and Allure, there isn't much Carnival can do presently to top that.