Well, actually, it makes one hell of a difference, go listen to a band like Extol, and then compare them to King Crimson or Jethro TUll, and tell me that there is no difference.
I know that they are a progressive death metal band, but it's kind of hard to tag them with that genre, since there isnt that much of it out there, but this album I just realized sounded like a 70's progressive rock album, which there is lots of other music that sounds a lot like it.