I find with some EQ tweaks on the MDR-7509/MZ-N707 combo that it's more listenable for long durations than the 7506/V6. As some of you may know, the 7509 sounds very similar if not identical to the V700. The V700 and the 7509 do go really loud from anything I've trid them with.
But for general short-term day to day portable listening, I'd give the 7506/V6 the thumbs up over the V700 in the US (in the UK where the 7506 can cost over 50% more than the V700, the recommendation is harder). It's got a much more upfront sound, slamming bass, is lighter and smaller. With the Beyer pads fitted, you'd look slightly stranger but it's more comfortable.
As for other closed alternatives, the HD280 looks a bit odd and lacks punch/bass with portables, and the DT250-80 is comparatively impractical for portable use. The D66 Eggos sound very balanced and good, but they don't seal out as much outside noise as all of the above.