A few facts about the LD:
The old Dolby Surround doesn't match what could be done with a strong 5.1 mix today, but it has good separation and some rich bass--which I found lacking on the DVD regardless of the mix, possibly due to compression.
What's most important about the LD, though, is that it is FULL SCREEN, while the LD has a matted screen which masks the image on the top and bottom but offers not a lot to the sides (it was not a Panavision film; it was shot in presumably standard ratio). Normally, a full screen version of a movie would be inferior, but for this film, you get to see things and perspectives that are hurt by their loss on the DVD (even if, in the theater, there was still *some* masking of the image depending on the location you saw it at).
It must also be noted that, from the outset, the mix--and later, mixes--were not entirely live; some studio or mix sweetening was done to many if not most of the tracks. Again, this is not necessarily a negative, because the band pretty much made their definitive versions of many of these tracks for this film, leaving some of the studio versions seeming to lack the vitality and presence heard here (which is fairly amazing when you consider how many times some of these were played by the Heads before they made the film).
I think this is one of the great concert movies. But I'm not sure the DVD lives up to that greatness in spite of the new mixes. I always come back to the LD, because of the reasons noted above. And, it's a big grungier and darker in look--think a more up-close approach to RUST NEVER SLEEPS--than the DVD seemed to me.
ED