There is really hardly even a noticable difference in the decor - they are nearly cookie cutter identical. Either one is a great ship.
Some of the few things are that are different, include the main show room production shows (which are some of the best at sea), the Royal Promenade Parades, and the ice shows (though some of the same concepts have been retained). There are menu updates and a few new programs, but for the most part, in terms of physical differences you will be hard-pressed to tell the two ships apart.
I am the editor, but I also speculate, ask questions and play devil's advocate. I reserve the right to change my mind.