You must try as many cruise lines as possible. How else do you determine what you like or don't like. Don't let one cruise line determine how you think. CCL, parent company of Carnival, Princess, & Holland America, doesn't want you sailing on Carnival forever. Carnival whets your appetite. Then you move up to Princess as you get older. Finally, when you are ready for a more traditional experience, and you don't want children running around, you move up to HAL. 3 choices to take your vacation $$$.
RCCL owns Royal Caribbean & Celebrity. Celebrity being the more refined experience.
NCCL spans the generations with their Freestyle experience.
I always hated when someone would post " I only sail Carnival because they are the best. I don't need to find out what I don't like ". This person is not qualified to say who is the best. It's okay to state why they always cruise Carnival, but shouldn't make comparisons.