I don't normally post reviews but in the case of MSC I found other people's opinions useful so thought I'd add my brief thoughts on MSC Fantasia.
We booked mainly because of an attractive itinerary that included a land tour to Machu Picchu with a price that was too good to miss. We joined at Barcelona with the itinerary including Malaga, Madeira, Tenerife, San Salvador de Bahia, Ilehus, Ilha Grande and Rio de Janeiro in Brazil.
Many of the reviews on this site for any MSC ship were alarming so I was worried the cruise might be a disaster. First impressions weren't good with a very slow embarkation prolonged by the fact that shore staff were more intested in chatting than giving me a boarding number.
Bigger than I expected. Adequately maintained but we hardly saw our steward over the two weeks. Bathroom OK. Storage good. TV from the 1970s, ancient, too small, not enough English language content.
Went to a turtle rescue project but it looked more like a mini turtle zoo and was mainly a visit to a shopping area with restaurants. Pleasant but probably not worth the drive.