Just back from a week on the Bellissima. It was amazing! 9 previous cruises with RC, first time with MSC and think we're converted.
We were mainly converted thanks to the food, RC is very American, and as MSC is Italian it's obvious via the food which was just amazing! Even the buffet was 10/10. The homemade piazzas 24hrs a day are AMAZING, compared to Sorrentos in RC. Yes the portions are smaller than RC in the main dining room but I like that, your're not too full and also means you can try more than one main if you want and not be too full. The entertainment was amazing, no comedians or magician due to so many languages, all musical but they're very good! There are entertainment staff that hang around with the passengers which are brilliant at getting people up dancing and enjoying themselves. We're a young couple and always disappointed in RC that the bars and nightclub don't really stay open past 1am, this cruise the music was going until 4am and always full of people dancing. The ports of call were all amazing, except Marseilles we weren't too impressed with. (Naples, Sicily, Malta, Genoa, Barcelona, Marseilles, day at sea, Naples, not in the correct order). Disembarking was so much better than RC, we didn't get off the ship until 2pm after lunch. Embarking was also so much faster and easier, as unlike RC where everyone gets on and off the same day, there are different people every day so its much faster.
The interior cabin is the biggest we've ever been in. So clean and modern, Zoe the interactive device you can use as a speaker for your music in the room by connecting to Bluetooth on your phone. The ship is very luxurious and the decor is really 10/10 beautiful, especially the promenade.