When it cimes to cruise value people do have different criteria and I know NLB has always preferred Carnival.
Carnival has made a point of remaining the most "inclusive" mainstream line - you find far fewer extra cost options on Carnival than you do on NCL or RCL.
If you are the kind of person who prefers to just stick to traditional cruising then Carnival is the line that has really changed the least in the last 10-20 years.
Mike M. likes NCL a lot because he likes the variety of cuisine available. I have to say some of the NCL meals I have had have been just amazingly good - I still think about a simple grilled ahi tuna sandwich I had on Epic all the time - it was the most delicious sandwich I have ever had.
But it was in the suite restaurant - I was eating with Roberto Martinoli and Doug Ward. I also luve the Brazilian Charruscaria - also on RCL's bigger ships now.