Just did a side by side with my DS Tungstens and my old LCD-X's. The first thing you immediately notice is the comfort, man does it feel awkward going back to the LCD-X's after the Tungstens, like the Tungstens aren't actually that much lighter I don't think, but but they truly feel so much more comfortable to wear.
As for the sound, I'm not an expert here and I'm not trained enough as other people are to know how to pick things apart but to my ears, the LCD-X's definitely have much more of an emphasis on sub-bass than the Tungsten's and you can feel that characteristic planar slam on them more, can't compare it them to the SS's which are said to have a touch more on the lowend, but where the Tungstens definitely win out on the LCD-X's is the details and soundstage, everything feels clearer on the Tungstens and the presentation is more spread out whereas the LCD-X's are much more packed-in and agressively in your face. Listening to something like EDM or Rock that's a lot more frenetic, the differences between the two are lessened, but if you put on something that has an emphasis on the vocals or something like jazz, and the gap definitely shows between the two.