I'd say that open v. closed will depend more on the environment. If you're frequently working around other people, are in a loud building, &c, closed is probably where you want to be. If you're well-isolated, you probably won't mind open headphones. I've personally always got a little creeped out sitting in a quiet room with closed headphones. Even if the only sound is fans blowing and keyboards & mice clicking, it's much better than total silence.
I do like the K702's, though you may want to be a touch careful. Very true (in my experience) that they have pretty lean bass, but to me they sound better than most loudspeakers at mid volume. At low volume, they have the same problems as loudspeakers (poor bass reproduction, distorted imaging) but when turned up, sound fantastic. I found them very comfortable (more-so than my regular Senn. HD-555's) and found bass reproduction better than those low/mid-range Senn's. Though to be fair, when amped properly, the HD-555's sounded pretty good in their own right. Other than that, I preferred male singers on the HD-555's and preferred, by far, female singers on the K-702's.
