I realize people on this site are probably seasoned cruisers but I will write this as a rookie because that's what I am. I just got off my second cruise. My first was with Carnival Fascination and my second was with Carnival Fantasy.
Both ships are ok. I don't think I'll ever travel with Fantasy again. It isn't anything big, it's a lot of little things that add up.
Fantasy is older and it shows. The staff are just a little bit less friendly and helpful. It's shopping (jewelry, clothes) didn't appeal to me as much as Fascination. The ships entertainment was not comparable. The show, trivia, etc. is higher quality and more fun on the Fascination.
Empress level is a good choice for me for most of the time. It is near most things happening on the ship yet not near enough to be noisy. It is one level down from our restaurant. It is definitely NOT the place to be in rough seas. I think the next time I cruise I will get a balcony. I really miss fresh air. I realize most seasoned cruisers spend very little time in their cabins, but I spend a fair amount of time there as I am a "homebody". Being alone in my own room is comforting to me. I want to be able to walk out of my room and be near the ocean. BTW - I sleep with my shades/curtains open in my bedroom at home because I don't like being closed in. I keep the curtains on the ocean view window open too.