I have been listening to both the blackwoods and vibro mkII these past two days. Definitely more different than I had expected. The blackwood doesn't need much or any more impact, its quite good there. Vibro too, but sometimes in different songs, there is definitely a different frequency that the bass is lifted at. The blackwood is very put-together and has a super coherent whole sound. The Vibro is a little more v-shaped, bass with some sparkle. Still, it is actually airier sounding, and sometimes it really excels at tracks that the blackwood sounds just like it does on most things. I think the blackwood is pretty versatile, yet I like how the vibro has a little more obvious dynamic shifts, and vocals have an airier quality. Both are really great. I'm actually surprised that the airiness of the vibro makes its staging and imaging a little more obvious and separated at times. Strangely my blackwood started acting up at some point today so I might not be able to do as much direct comparison as I'd like.
If I had a complaint about the Vibro it would be that it needs more clamping pressure, its a bit finicky on the head. Maybe it would do well with the cowhide pads, seeing as I really like the fit of the blackwoods, but it may just be the different headbands used. Still it is one heck of a closed headphone. Glad I picked it up, especially considering the Blackwood may be making a trip out to Chicago.