I just got back from Sailing the Infinity and the food was marvelous... I am an excessively picky eater, but i could find something each night on the menu that satisfied me to the fullest, the Tiaramisu (spelling?) was exquisite. The 2 corn soups they served were So delicious i asked for seconds of both...
I find sailing RCI during Holidays actually gives you better food. I have never had a bad RCI experience, however the filet mignon is in my experience always been tough... and their deserts leave something to be desired. I don't like the fact they switched to the dining room lunch menu always the same, sort of boring...
The buffets on both are comparable (but chicken parmigiana on Celebrity... is not what I am used to) Both Good with some superb choices and some not so superb choices.
I am not a fan of the Carnival Ecstasy's dining experience, escargot was over done, Steaks were always tough and most of the time overcooked... and serving baby back ribs in the fine dining room is a bit strange... delicious but strange. None of their soups tickled my fancy they tasted watered down.
so Best to Worst
1. Celebrity by FAR
3. Carnival Ecstasy (shudders in remembrance)
HOWEVER for the best Chocolate Ice Cream on the High Seas...
Royal Caribbean Blows the other two away... just in case you want to make your cruise decisions based on Chocolate Ice Cream