My choice would be the Eastern Caribbean on Carnival. Each cruise has it's own personality but the Caribbean is always a favorite. You will find deck parties on NCL (weather permiting) but no singing waiters.
56 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 X2, Breeze, Sunshine X3
7 Norwegian: Sky, Jewel, Dawn, Epic, Pearl, Breakaway, Getaway
7 Windjammer: S/V Legacy X3, S/V Polynesia, S/V Caledonia, S/V Diamant, S/V Sagitta