Both GWT and Wicket are stateful, java object oriented based. GWT is completely client based with features like javascript optimization, CSS optimization, and I\'m pretty new to
Wicket is server framework. It allow to create html which you needed. It is possible separation of roles in project. (Web design->html/css->java).
If you consider to use GWT for you project, web designer probably not needed.
GWT generate javascript. Most logic can be executed on browser side. GWT better for scalable application.