I go with the best price and itinerary. I have sailed with most other lines, first time with Carnival. I have avoided them because I am not a big party person. The ship was nice, a lot of brown decor I don't care for brown. But the food, the service and the entertainment was about the same as with the others I have cruised with. The entertainment was a bit different, they had the song and dance stuff every night with the same singers. My other trips they have had more variety, song and dance, magicians, jugglers, comedians etc. The Conquest had comedians in one of the lounges and they were okay but not great. The waiters were great as was the cabin steward. The excursions from the ship were pricey. You can do a lot better online or just getting off the ship and hook up with the swarm at the ports.
When the weather was rough the cabin creaked badly, difficult to sleep.