We always sail concierge, both on DCL and RCCL, so I'm happy to provide comparisons if you're interested.
RCCL's setup is more like the newer DCL ships in that there is an actual concierge lounge, where you will find your concierges at certain hours (and bartenders during happy hour.) There are free drinks (alcoholic beverages and sodas) during happy hour, as well as assorted appetizers, both hot and cold. Some of the RCCL's concierge lounges double as the Diamond Lounges (RCCL's frequent cruiser program), some are just concierge lounges. The ones that double as the diamond lounges can get very crowded during happy hour. The lounge doors require a keycard for an appropriate room (or cruiser type, as diamond + may have access.) In my experience, the lounges seem to have snacks often through the day (continental breakfast in the morning, cookies in the afternoon, and serious appetizers at dinner time.) There is a coffee machine in the lounge that is always available; we thought it served the best coffee on the ships.
My favorite RCCL concierge perk that I really miss on DCL is that there is reserved seating for the shows for concierge guests. It is not the best seating in the house, but it is held open for concierge guests until something like 5 or 10 minutes before the show, so you can be secure you'll have decent seats without showing up way in advance. We loved this, and used it constantly for the main theater shows. We also got guaranteed seating in the ice skating shows. The ice skating shows are absolutely amazing, and remain some of the best entertainment on the sea (in the opinion of everyone in our family. Oh, except the 3 year old, because well, no princesses.
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Another RCCL perk we've liked a lot was that for your final disembarkation, the concierge would gather the group of concierge guests who were ready early, and escort them off the ship first. The kept you from getting stuck in the long customs line that could sometimes develop.
As far as meals go, we got our choice of times at all the specialty restaurants. (This was also true concierge on DCL.) The full dining room menu is available for room service. (Also true on DCL.) There is a reserved area for breakfast and lunch for concierge guests, so even when we were grabbing a quick bite, we didn't have to search for a table.
We've found the service on RCCL to be great sometimes, and terrible sometimes. We had a really bad experience with a terrible wait team when we did anytime dining, and we got them twice. We hated anytime dining, in part because of them. We'd had such good wait teams on other cruises that the differences were very obvious. On RCCL, we've had teams who learned our drink preferences by the second night, and had them all waiting for us when we arrived at our table for almost the entirety of the cruise. We've had teams who made sure our toddler or young child had food or snacks waiting for us when we arrived. (We've traveled extensively with very young children, so these things really mattered to us - DS's first cruise was at 8 months, DD's was at 14 months.) We've had teams figure out my DH or DM's favorite dessert, and bring them one almost every night in addition to whatever they actually ordered.
We've also had great experiences on DCL. Our most interesting experience in the MDR on DCL was that we observed the table next to us getting gorgeous, obviously freshly cooked Indian vegetarian food night after night, and we commented to our team that we thought it looked and smelled delicious. The next night, they brought us several specially cooked Indian dishes, a mix of vegetarian and non-vegetarian options. We were blown away. (A couple of the dishes were some of the best we had on the cruise, even eating Palo meals multiple times.)
As far as what is included, with any cruise, doesn't matter what cruiseline or what cabin type, your basic meals are included. Almost all lines (including both RCCL and DCL) will have both a main dining room (MDR) option and a buffet option, as well as various quick service places that have things like pizza or hot dogs. DCL is unique in the fact that their main dining room is actually 3 smaller dining rooms that you rotate through, each with different decor and a different feel. Almost all lines these days (again, including both) also have specialty restaurants that you can pay extra to go to. The real difference here is that food in the MDRs is prepared in bulk, so it like eating at a nice banquet. It is mass produced. In the specialty restaurants, your food is generally cooked to order. This does generally make for higher quality of food in the specialty restaurants. Some people consider the extra nudge in quality worth it, others don't. In the main dining room, depending on the size of your party, you may be seated with other travelers. Unless you're in concierge; concierge guests get their own table, generally, unless they request otherwise. In specialty restaurants, you will be seated at your own table, unless you are attending a special program, such as a wine dinner or visiting chef dinner, in which case everyone may be at a single large table.
As far as drinks go, most lines have tea and coffee included, and often juice at breakfast (but not fresh squeezed juice; that's extra.) Coffee drinks are usually available for purchase these days from a coffee bar. Disney includes soda from the beverage station. (Cans are still extra.) Other lines charge for each soda, or you can purchase a soda card.
Small snacks are generally available around the ship and at the coffee bar, but some (such as premium ice cream or cupcakes) may be an additional charge. You can usually grab things like pizza and burgers for free through most of the day, as well. (RCCL ships also often have a johnny rockets on the ship these days, which charges both a fee to eat there AND an additional fee for the milkshakes.) Sometimes they offer some of the dishes from the specialty restaurants in the main dining room for a small upcharge, as well.
Anyway, all you can eat is definitely included. You can expand your options by spending extra money.
Entertainment is also included on the ships. This can include movies, variety acts, classes, production shows, and lounges. Bingo and, on RCCL, traditional gambling, costs you extra. Shore excursions cost extra. (You can get off the ship on your own and grab a taxi or book excursions independently if you want.) On RCCL ships that have them, flowriders, zip lines, ice skating (they provide the skates), mini golf and rock walls are included in your fare.
We haven't done the Dreamworks experiences, so I can't speak to them.
Hope some of this is helpful!
