I had no idea the older Batman dvds had the better audio. I did sort of wonder this when I was buying Batman on dvd as I remembered that some of my older dvds had better audio than the later releases. I think what stopped me buying the older dvd of Batman was seeing that the new edition had a DTS track. Unfortunately the DTS wasn't nearly as impressive as I was hoping.

By the way, Batman Forever is a weird one. All the releases sound different to me. I remember staying up late one night going through the same scene with different audio on different releases. I could be wrong, but then it was a while ago..