If you click the big yellow button Cruise Reviews & then choose MSC from the drop down list you can read the good, the bad & the ugly. In terms of rating them against your choices, RCI & Celebrity are in a different league to MSC. I can't help with Thomson but they get constantly good reviews albeit they are older ships, & Costa would need to be offering free cruises & limo transfers to get a response from me. The reviews say it all. The New ships are lovely, exceptionally clean, good service, school dinners, chaotic organisation, but good value for money. RCI are 4 star Celebrity are 5 star MSC are 3 star so keep any expectations at that level. Regards Wiba.
Take every cruise as it comes and enjoy the best moments and try to ignore the worst and there are very few of them.