If you like Carnival I think you will like NCL. In my opinion each has certain things that they do better than the other. Give them a try. We usually go Carnival but intend to mix in a few NCL.
52 Carnival: Mardi Gras, Ecstasy X2, Fascination X6, Celebration, Elation X5, Glory X5, Fantasy X4, Valor, Holiday X3, Imagination, Liberty, Spirit X2, Freedom, Destiny X2, Splendor X2, Dream X2, Conquest, Legend X3, Victory, Sensation, Paradise, Inspiration, Magic X2, Triumph, Miracle, Breeze
6 Norwegian: Sky, Jewel, Dawn, Epic, Pearl, Breakaway
7 Windjammer: S/V Legacy X3, S/V Polynesia, S/V Caledonia, S/V Diamant, S/V Sagitta