I know about DVD Beaver's screen capture comparisons, but is there a website which compares various releases of Disney titles? Apart from extras, I'd like to see which titles are worthy of upgrading from previous releases (IE; PETER PAN, TOY STORY, THE LITTLE MERMAID, LADY AND THE TRAMP, DUMBO, ETC.)

Well, it's not Disney specific and doesn't have screen comparisons, but Dvdcompare is pretty good about listing the elements of different releases.

Dvdcompare

It is currently down for maintenance until 02-Jan.

Ultimate Disney might be helpful too.