Hello, I spent 41 nights on HAL last year, and 20 of those on the Rotterdam. I also spent 20 nights on Carnival last year. It was a great year for my cruising. I love HAL, it's a notch or two above Carnival. FOR me, HAL has steps into the pool, which is something I need. The food is better, the children are less, it's a 'more adult' kind of cruise.
Carnival has the best sail away party, HAL will be quiet and more reserved. You always see and hear the Carnival CD, you will not get the same from HAL. I love longer cruises, advantage HAL. I wish you the best of luck whatever you deside. I would suggest giving HAL a try. Any questions feel free to ask. Debbie