This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
There is no universal "best"--just like Bear said, "best" is subjective, and depends on many factors.
None of these are Struts questions, however. If you have further questions regarding non-Struts, client-side frameworks you should ask them in the appropriate forum.