We have cruised with 11 different cruise lines and are in all the repeater clubs including RCI Diamond, Celebrity Elite, Princess Platinum etc. IMHO the best, by far, is RCI once you reach the Diamond level. Why? It gets you unlimited access to the Concierge Lounge which has 24 hour expresso/cappucino (its a real high tech computerized machine that really works), and also allows you to attend the daily cocktail hour (usually 5-9) which included free drinks and decent munchies. Tender priorty (Princess, RCI, HA and just about all the lines) is great for those of us who like to do our own thing on shore.