My DW and I have been on the Freedom of the Seas twice (our first two cruises ever), then the Allure of the Seas, the Independence of the Seas (a 4 day Thanksgiving cruise), and the Harmony of the Seas.
We loved the Freedom. We thought that the Freedom would be the biggest, but we wanted to try the Allure. We feel in love with the Oasis class ships. We have a cruise on the Oasis booked for April, 2020.
I understand that a lot of people think that the size is a big turn off or that the itineraries are lacking. the Oasis class ships are limited on the ports that they can visit, but as someone earlier said, the ship is the destination.
Remember there are about 6300 passengers on an Oasis class ship, making reservations for the shows are a must. My wife and I never fly but the seat of our pants. We always plan what we are going to do starting about a year before the cruise. In fact next Sunday will be a year till our 2020 cruise, so we will start some planning and preliminary list making.