54 and 61 here. We loved Harmony. It is bigger, so you MUST pre-reserve your big shows (aqua, ice show, grease) before your cruise (watch the app). Then, when you board, you reserve the other shows (comedy, etc) first thing. Then, you also reserve your dining package restaurants first thing. You can see it is important to get an early boarding time - so be sure to "check in" the day that opens up as well. As for crowds - it will be a LOT more people, but there is a LOT more to do - so it will be very spaced out in the evening (some are at shows, some are at the music hall, some are at Karaoke, some at Piano bar, others at boleros, etc...) Definitely see Grease on board... it is just AWESOME! Enjoy the Central Park area for coffees (park cafe) and drinks (outdoor trellis bar) and evening entertainment.