I think a large part of the difference in sound is down to the production qaulity and of course influence sat the time. Alot of there new stuff and the whole EBW series have so many squeeks and blips, sirens, space ships, monkeys, whistels, you name tom & Ed prob effect it somewhere in there songs.
I think they are still similar music its just that they can now convert their ideas better onto vinyl so we get a higher/smoother sound.
Exit Planet Dust: Produced mostly on Tom's equipment at home
Dig your own hole: Brothers still learning to play with equpment more power less crackle:samples are better
Surrender: better production if a little trance like
Come with uS: The differnce in actual production quality is massive I think to early Albums.
I think this theory holds up with Acid Children, its got the dark and punchy acid sound but it also has the really crisp production.
Laters
p5