See: http://dev.itmill.com/wiki/Articles/ComparingToolkitWithIcefaces
(sorry to bring up an old thread)
The article has been moved to a new location:
http://vaadin.com/wiki/-/wiki/Main/Comparing%20Vaadin%20with%20Icefaces?p_r_p_185834411_title=Comparing%20Vaadin%20with%20Icefaces
Check out the comparison matrix also where multiple different frameworks are compared side-by-side:
http:://vaadin.com/comparison