I don't have as much experience with cruising as some on here, but we've sailed the Carnival Breeze (September 2016) followed by the Disney Wonder (January 2017) very recently and it wasn't that long ago we were on the RCCL Freedom of the Seas.
We love
DCL because we love Disney, but we don't love everything about DCL. We found the Carnival Breeze to be surprisgly nice and much better than any Disney ship in a few areas. We loved their "food court" and the subsequent variety and we loved their prices. We stayed in a Jr. Suite for less than DCL aft whitewall Verandah. DCL shows are far superior and we thought the MDR experience on Disney to also be much better than the Breeze. The overall ship decor on Disney is outstanding and the guests are treated exceptionally well.
The Carnival Breeze sold me on Carnival as being a very viable option for us. We had sailed older Carnival ships and were not very impressed. Our advice previously was to stay away from Carnival unless you could not afford anything else and just had to get on a ship. Now I would find them to be an acceptable alternative, but only on their newer ships.
The biggest thing to look at is the age and size of the ship. Then look at the cruise line. You must find an itinerary you prefer as well, but I would not cruise to Hawaii or around Hawaii. It sounds novel, but the amount of time at sea is much more than you might think and you'll be sailing in the Pacific, where there is a great chance of rough seas if you cruise to Hawaii.
If you are a fan of Disney and really like the Disney experience (uniquely Disney), then there is no other choice but DCL. You can get great service elsewhere, but Disney has a way of just making the service feel special. It's not stuffy, but relaxed and fun but so polite and helpful. Nobody else has the kind of training that gets this type of balance.
If you are looking for a great vacation experience and are interested in Disney because you heard it is "better", check elsewhere. You will pay a premium for DCL and unless you really appreciate Disney, you can get better bang for your buck with RCCL or even one of Carnival's newer ships.