Its hard to beat some of the Royal Caribbean's larger ships. They offer so many more activities than I found on Carnival. Food is about the same as well as entertainment. You'll find the parades and ice shows to be superb on Royal Caribbean and I thought the service level was higher on RCL than Carnival.
If you like to do more things while cruising, check out the new Freedom class ships, wonderful if you are cruising with family and kids. I love their pool decks better on these ships, never had a problem finding and lounge chairs and the kids have their own pool area, which was great.
Royal Caribbean just seems to work better for me, I think its worth a try for you, bet you like it.