I haven't got my mad dogs anymore for direct comparison but I'll try from memory. The impression is kind of against each other so it may sound slightly exaggerated. Sorry if I offend anyone, this is just IMO.
The highs of the TH600s extend way way further than the mad dogs, and on some tracks it may sound almost sibilant. Theres alot of energy in the highs of the TH600 and the cymbals sound very alive. The mad dogs highs sound relatively rolled off in comparison. The mids of the mad dogs are a bit more forward than the TH600s and I don't know how to explain it but to me sounds quite a a bit thicker. The TH600s mids sound OK on their own and you get used to it once you've had it on your ear for a while but in comparison, the mad dogs have a meatier mid (this is not that relevant when listening to EDM, as the mids aren't affected as much and you don't notice it so much when there aren't any vocals). The bass is where the TH600s has it all over the Mad Dogs. The bass extension, the bass quanity, the bass texture (in both sub and mid-bass) is the best I've ever heard. It may be a bit coloured and anything but neutral, but those drivers and magnesium alloy cans sure give the TH600 something special in the way of bass, and there is absolutely no bleeding of the bass into the mids, theres so much separation. The mad dogs in comparison sounds feeble in the way it presents bass, it's missing the slam and extension I'm after when listening to EDM.
In comparison, if the Mad dogs are a flat neutral can, the TH600 is a U shape with extended highs and bass, and a somewhat thin mid section.
Other things: The soundstage of the TH600 is so wide and unbelievable for a closed can, its at least twice as wide as the mad dogs and wider than my HD600 and HE500s which are open.
The Mad Dogs are more comfy than the TH600s, although the TH600s aren't that uncomfortable, the mad dogs are probably the most comfortable cans I've ever tried. The mad dogs isolate better than the TH600s and although the TH600s are closed, they do not isolate nearly as well. They donn't leak sound, but you can hear things around you almost like an open can.
In listening to EDM, the mad dogs sound like something is missing when compared to the TH600s, the TH600s presents the music with so much energy that it makes the mad dogs sound quite dark and lifeless. But I have to say that the mad dogs is a can that takes getting use to as well (when I first got them, I though they were broken - coming from HE500s). It takes a while to get over how dark it is, and once you do, it can sound pretty special especially for other genres like rock and vocals stuff. I'd say the mad dogs are better for anything else that's non-EDM. Since I listen mainly to EDM the TH600s seem like they are made for me. It was a tough decision letting go of my mad dogs but I had to since they weren't getting nearly enough time on my head.