I've never been on the Majesty of the Seas so I can't give any first hand information on that ship. From the friends I know who've sailed RCCL and Carnival, they prefered Carnival. I guess it really depends on your personal preference. They said Carnival offered more night life and more activities overall. RCCL was more laid back. They also said the rooms on RCCL are really small. Again, I've never been on any RCCL ships so I don't know first hand.
As for the Fascination...I really enjoyed myself both times. Everything was always clean and in order and the crew was wonderful. They were always friendly and very helpful. This has been my experience each time I've cruised. My first time on the Fascination I cruised with my sister. Carnival fell a little short in a couple of areas (compared to the other cruises) but we still had a wonderful time. I posted a review for that cruise.
http://www.cruise-addicts.com/reviews/readreview.php?id=0000004056
I chose the Fascination the second time because it was a convienent quick get away and what a better way to get away for the weekend than to go on a cruise. When I took that cruise in April, I cruised solo. I again had a wonderful time. I feel like the crew paid closer attention to me since I was cruising solo. The food was much better this time. As I stated in my review from the January cruise, my sister and I believe they had a new cooking crew on the ship in January.
Overall, I had a great time on both cruises. I hope this information helps.
Gloria