Gummo was nothing more than a bunch of ******ed kids going around torturing cats. Nothing more, nothing less. That's not disturbing... it's disgusting. It's just a horrible, horrible film.
Martyrs, on the other hand, is genuinely disturbing and a good movie at the same time. Martyrs actually makes you think and brings real emotion out of you, feeling for these characters going through such terrible experiences. And with Martyrs you actually get to dwell into why these terrible things are happening; there's not a single moment in Gummo where you get that, because it's a no-good, piece of shit film that only exist to exist. There's no point to it, and it serves no purpose. To me, that makes Gummo worthless, not disturbing.