Food is better on Carnival ships than RC or Norwegian. (I recommend all the restaurants!) The variety of foods is m-u-c-h better!
Staff is friendlier on Carnival. I was so impressed, I tipped our cabin steward an extra $20, our dinner waitstaff $10 each and our wine steward $10 - and I have never - ever tipped anyone extra above the 'required' amount.
Entertainment is better on Carnival. The singers were was amazingly talented - much better performers than any other cruise we know of.
loud noises all night from the deck above as staff moved chairs - the noise reverberated thru the steel floors disturbing our rest each night, several times each night.