They all pretty much offer the same. Theater, bars, casino, pool, buffets, restaurants etc... The differences is in the sizes, layouts and decor and that's really what makes it exiting to cruise the different ships.
Carnivals ships are grouped into different classes where the ships in each class has almost the same size and layout, but different decor.

There is a great description of all Carnivals classes and ships on Wikipedia here

So if you want to experience the difference in the ships then you'll make sure to cruise on another class on your next cruise.

Thanks for replying! Can't wait until we sail away again. 

Once you narrow it down to a few choices, let us know what you’re looking at and maybe we can tell you some of the differences.  Happy cruising!

 

Hi,

 

Yes, although most of the activities are the same, shows, pool area, etc... may be more elaborate on the larger ships.  Even the passengers may differ from one ship to another - longer cruises vs. shorter cruises.  Even when you travel makes a difference.  Around shool holidays you will have many more kids and families onboard.  The bigger ships are newer with newer technology.  Find a ship class that you like - not what someone like me likes. I perfer to look at the itinerary and cost when deciding.  But, then again, I booked the Breeze Transatlantic just to experience the new ship.  This time that was all that influenced me.

Some Carnival ships have features others don't. For example, none of the Fantasy Class ships(Carnival Fantasy, Imagination, etc) and the Spirit Class ships(Carnival Spirit, Pride, Legend, Miracle) have the Carnival Seaside Theater which is the large outdoor movie screen over the midship pool.
The Fantasy Class ships, Destiny Class, and Triumph Class ships(Carnival Triumph & Victory) do not have Steakhouses(Specialty Dining).