This is the reason above all to see DLP ... it's like watching a DVD on hi-def TV, but one that's 2 stories tall. Now, if they only had DLP IMAX ... what an experience that would be.
I think we get different "versions" because Lucas is an incessant tinkerer. Since he could tweak Ep II further before the DLP release, he did. Some of the changes were good (Padme's "getting up" scene was more believable) and some were bad (I'm a Jedi, I know I'm better than this).
If there are different versions of Ep III, then it's highly likely that the DLP version is what will go to DVD.