QQQ, maybe be a little bit more constructive with your responses? Things like, "Neither" or "There's better..." don't really help the conversation.
At any rate, if its between these 2 phones, I would say the DT990 would be a better choice. The large soundstage and lack of power (not depth) in the bass of the K701s don't work well with metal, in my opinion. The DT990 has a very satisfying amount of low-end impact, which I think adds to the double-bass drum and palm-muted guitars in a lot of metal. I find the mids of the of DT990s quite recessed, but that may be a benefit as many metal guitar players go the "scooped mids" route on their amps anyway.
I like the K701's huge soundstage better for gaming, but the DT990s aren't bad in this area by any means. I generally reach for the HD-580s when I game, but I wouldn't mind using the DT990s.
I think both headphones are comfortable, as I don't have a problem having either on for hours at a time, but the DT990s are a phone I can put on and forget that they're there. Probably the most comfortable of any headphone I have used.