As far as onboard experience goes, My family considers food first. RC has a fair dinner menu in the MDR, although the quality could be a bit better. Their buffet is wonderful in terms of selection, quality and they change things up daily (not all things). And they have very good specialty restaurants. Carnival was much worse, especially at the buffet - it was always the same stuff. Disney, on the other hand was much better in the MDR. But for 50% more for the cruise is it worth It? Now that my boys are teens - I would say no. Celebrity and Princess are supposed to have better food, but the extra cost to cruise again begs the question - is it worth It?
As far as entertainment and activities to do while on the ship, I think RC has all the others beat. There is too much to do in fact. On the quantum class and oasis class, you could literally split yourself into 4 to do stuff all over the ship.
I think the storeroom attendants are helpful and kind no matter who you cruise with. I know the average storeroom is a bit bigger on Disney, but that is because most people sail with their kids in the same room.
As for the bars and lounges, the are pretty much the same on any cruise line. But I do want to try the bar on Allure that goes from the promenade to central park.
I would do it onboard for 2 reasons: to pay the reduced deposit and you normally get an onboard credit when you book as well, plus any other sale RC has at that time. The will ask you for a travel agents name, if you like, as well at time of booking.