I doubt whether or not even Windu could stand up to the Emperor in a light sabre dual.. Though, they never exactly show to what extent Palps was feining weakness in their dual, I would assume that the whole fight was orchestrated. Had he wished to kill Windu as quickly as the other 3 Jedi\'s, he would have done so.
I\'m pretty sure it would only have been Yoda, and maybe Anakin.. had ne not lost his cool in a hypothetical fight as he did against OB1.
Oh, and I forgot who mentioned it, but the point of Yoda bringing up the ability to comminicate from within the Force is a perfect way of explaining how OB1 could communicate with Luke after death (Remember, the force.. will be with you) and how Anakin, Yoda and OB1 were visible after death.