I have not sailed on Costa in Europe but I hear Costa is not going to come to the caribbean that much anymore - European cruising is really taking off. They will only have one ship in the caribbean next year. I believe it will be the Fortuna.
The bigger question now is should you take Costa in Europe. If you like the price and itinerary I say you should - as long as you have a companion and dont care if you meet people on the ship. Keep in mind you will be a minority, so it is an Italian experience even upon the ship. Some people might find that enticing, some might not.
As long as you like veal, lamb, octopus, etc, then you will like the food. Don't expect to see steak every night. There was no pool hamburger bar - just pizza on the Deliziosa.