I love northern flora and viking culture and imo Scourge is a more interesting enemy faction than Twilight's Hammer. Also I liked Ulduar's style, whereas I don't like Egyptian architecture that will heavily inspire Uldum. Arthas is one of my favorite villains of all time as well, though Deathwing is pretty awesome too.
Why I still think Cataclysm will be better? Simply because it reintroduces us to the old world, a place where we old hats played before the expansions, only now we can fly and everything has evolved. Secondly, the Horde vs Alliance war, it's my favorite Warcraft feature.