I have only been on two cruises in my life. I have been on Royal Caribbeans Sovereign/Seas and a year later, Carnival's Inspiration.
It is hard for me to say which one was better. It seems if they were evenly matched.
I did like the food better on Carnival. It seeemed as if it was fresher and more attention was given to it's presentation. I also liked all that Pizza and Ice Cream they had in the Lido Cafteria.
However, I was on the Sovereign, just one week prior to her major multimillion dollar renovations. So I missed out on those famous national-chain restaurants she now has on her Lido Deck: Johnnie Rocket's, Sorrentos, Ben&Jerry's.
I liked the Inspiration better than the Sovereign in terms of ammenities. My cabin on the Inspiration was way bigger (167 ft2 as opposed to the Sovereign's 115 ft2). I liked the interior decor of the Inspiration better than the Sovereign. Some people seemed not to like Carnival's interiors claiming they look like an over-the-top glitzy vegas casino look. I did not get that impression. However, the Sovereign is an older ship (built in '88) as opposed to the Inspiration being built in '96. Also, allot of the Sovereign was off limits during my cruise to to some of the renovations were already underway.
As for the entertainment, both ships had really great entertainment and very talented performers. However, I would give the edge to the Sovereign. It seemed as if they had a more classy form of entertainment and made more of an effort. I really didn't care for Carnival's mascot in their shows. It just seemed a little cheesy for Carnival to do self-promotion during the shows.
When it comes down to the overall expierience, I would say I had a better time on my second cruise (aboard the Inspiration). Although it is totaly subjective. Also other factors not related to the differences in the cruiselines, could have been involved: it was my second cruise so I was better prepared, the ports of call were different (better?), the Inspiration was not underconstruction during the cruise. So like I said, it was a close match and a subjective opinion of mine. If you were on both cruises you may have had totally different expieriences and subsequent opinions. Either way, cruising is what you make of it, if you are looking for a good time you will find it. The same is true with looking for a bad time.