I am torn between Wicket and Vaadin. I am starting a micro-isv and need to make a choice of web framework. I have narrowed down my choices to Wicket and Vaadin. I have used both
I am currently working with Wicket and I have worked in the pass with Vaadin. I wil be short in my observations:
Appart from that, we are talking about two different types of frameworks, two different approach, which have pros and cons that I advice you to search and compare and see what really fits your needs.
Edit: Oh, and about the look and feel, for instance you always have Wicket Bootstrap