I have only been on the Carnival Fantasy and now the Sovereign. This will be easier if I just compare the two. Parking and boarding were easy on both ships. This is where the similarities end. The cabin (6581) on the Sovereign was tiny and smelled like sewage from the moment we boarded. When we asked the cabin steward about the smell he said that it was because we were still in port. Well the odor never left us but I think we actually got used to it. It was much better if we kept the bathroom door shut. The Kismet dining room was pretty nice but the service did not compare to the Fantasy. The food in the dining room was good and compared pretty much to the fantasy's food quality.
The windjammer cafe was hit and miss. The biggest difference was again the service. On the Fantasy the staff was everywhere and when you finished with a plate or a glass they were to take it away. The Fantasy staff also always offered to get you another drink or anything you wanted. On the Sovereign we watched two crew members talking and laughing while almost every empty table was piled with dirty dishes. One morning I had bacon that I'm sure was spoiled or at least the worst tasting bacon I've ever had. The two ships are similar in size bit I thought the Sovereign was laid out a little nicer. On the last night our toilet stopped working at about 4am on Port Canaveral morning.
We had already tipped our cabin steward so he did not care at all about our problem. The pursers desk said that they would send maintenance but we never saw them before we left the room at 8:20 am. We had to use the public restroom that morning. Have I said enough? The two experiences in fact do not compare.