While the Carlton 2-DVD release offers both the original theatrical cut and the extended version of the film (kicking off with the gathering of Himmler, Canaris and Hitler in Bavaria which led to the fateful chain of events), this only offers the extended version. I personally think the post-production guys were almost fully justified in the cuts and in substituting the original opening with the documentary footage for the pre-credits sequence: the documentary footage is both pithier and also more immediately creates a sense that this story 'could have happened' (rather than presenting us with an embarrassing impersonation of Hitler). In short, the theatrical version is pacier, and doesn't give us so much time to reflect on the slightly absurd premise of the story.
On the other hand, there's at least two scenes cut for the theatrical release which in fact make more sense of the story: one is a brief meeting between Colonel Radl (Robert Duvall) and his doctor, where it's clear that his health is precarious - so making sense of his line towards the end of the film, 'I was measured for my casket months ago'; the other (more often noted) is the meeting between Joanna Gray, Liam Devlin and Colonel Steiner where they recap their plan.
So I suggest that those who already have the Carlton double-disc set are pretty well off and certainly shouldn't trade it in. However, this new ITV DVD set offers far more extensive documentary footage on making the film as 'extras'; both contemporary with the actual film-making (some of which is included on the Carlton, though not including the brief on-location footage in Norfolk), and also (not included in the Carlton set) a visit to the actual village as it is today where the film was made: this includes some fascinating views of the designs used to extend the original mill, adding the crucial mill-wheel and the part of the building that gets finally bazooka'd; also some interesting anecdotes about how the special effects and explosions were managed in and around the real-life church. For those extras I imagine all devoted fans of EHL will want this set as well as the Carlton.