I'd like to hear the difference myself. I'm not super happy with LX at the moment, having just rebuilt mine after 1000 miles (slow day just wanted to look around in there), and found a broken labyrinth and a rough race.
XT and LX tend to get lumped together for touring purposes, and my LBS which does a lot of touring bikes, was not inclined to go any higher than the LX. They recommended buying the cheapest hub that was made outside China in the Shimano line, or something like that. Beckman lumps them together, calls them good quality, though says they are not great for Clydesdales or "expedition" use.