Masirimso3 said:

That's fine, however in my opinion the duel of Bespin would work very well with action music, a portion of used it did too, the middle portion, with The Clash of the Lightsabers. Without Duel of the Fates it still works but not much would change. Duel of the Fates gives more excitement to it in my opinion.

While music can sometimes make a scene more exciting, other times though (depending on the mood and what's happening in a scene), no music can have its own positive reward and therefore be the better choice. In the case of Luke's initial confrontation with Vader in the freezing chamber, no music there makes the scene more ominous in an already haunting environment. Our ears really hone in on all the details around - the steam and other subtle background elements, Vader's breathing, then the duel itself - it's a very thrilling experience of its own really :)