I have a slight preference for Clash of Kings over Game of Thrones, although the two are quite close. In my opinion, Clash of Kings doesn't have a plot that is as tightly connected as that of Game of Thrones. This is because it lacks central mysteries that drive and connect the plot to the same extent. However, I believe that基本上 every point-of-view (PoV) character in Clash of Kings is more interesting than their counterparts in A Game of Thrones.
Probably my favorite books featuring Tyrion and Arya are in Clash of Kings. The entire back half of the book is truly amazing. The Battle of Blackwater is simply awesome, and the chapters featuring Bran are also there. It's these elements that make Clash of Kings a great read and just edge it ahead of Game of Thrones for me. Overall, I rate it 9.2 out of 10.