Hi, We also became Elite on Celebrity and then we were Diamond on our first RCL cruise (which was 3, two weeks each B2B2B). WOW!! what a difference. The Elite happy hour is poor compared to the Diamond lounge. With Celebrity they walk around with small trays of stale crackers with a small piece of stale cheese. By time they reach you the plate is empty!. Also they walk around with a tray of limited types of drinks. If you order something else it takes forever to get your drink.
Also, I think? that the Diamond lounge is opened earlier and longer than Elite.
Now with RCL: They have several buffets of food. Outstanding. Both hot and cold. Examples (but not on all cruises): Bacon covered scallops, chicken on a stick, chicken wings, egg rolls, meat balls, chocolate (dark and white) covered strawberries etc. I'm getting hungry writing this! Sometimes we even miss dinner since the buffet is GREAT! Also they take drink orders and service is FAST. A dollar tip (which we always give!) will also bring them back within minutes if your thirsty. They have an over abundance of waiters. If you can't wait you can go to the open bar and order a drink quickly. We are NOT alcoholics and NEVER drink at home but it's nice to have a drink on a cruise especially when I'm not driving! It's hard to believe that RCL and Celebrity are owned by the same company and Celebrity is suppose to be the upscaled version of RCL. Go figure! Because of this (and the low low prices of TA's) usually many Diamonds go on these TA cruises. They know excellent value for your $$ when they see it!!
Also getting to/from Europe without jet lag makes the vacation more fun. We also have been on many TA's and the Diamond lounge is crowded but still GREAT. When this happens they usually open another adjacent lounge and load your card with 3 free drinks so you can go to other bars (but you still have to go to the lounge or the buffet). We now do mostly RCL and few Celebrity cruises. These opinions are mine and my wife and some of you may disagree with what I say. Sorry in advance. LOVE being Diamond!! Bill & Gloria