I finally got a working pair of these today. The first pair I received had an awful sound leak in one ear, but meelec replaced it really quickly. They really have top notch customer service.
Anyway, from what I could tell from the other pair and from listening to these (though they aren't properly burned in yet) is that while they do have massive amounts of bass, they're not as clear as the GR06. If you're listening to EDM and have those songs that hit hard, the M-Duos can make your head absolutely shake, but I think they sound a little cold. I'm assuming that's because of the recessed mids. They remind me a lot of the SuperFI 5 EB, only more comfortable. In truth, that's where I think they beat the VSonic. I don't especially love the way the GR06 and 07 fit, but I know there are many who do.
Anyway, that's my brief take on the M-Duo, now that I have a fully functioning pair. I may change my mind a bit once they're burned in for about 30~40 hours.