As I'm a huge EDM fan myself, I found the V6-Stage sufficient for most tracks. There is some sub-bass rumble, and mid-bass quantity is adequate to provide a punchy, fun sound for general EDM tunes.
However, if you must have an inherent bassy pulse, then the V8 is more satisfying. I tested the V8 (and the V6S) with various EDM tracks from a few genres, including Hard Trance, Hard Style, Gabber and Eurodance. The well-textured bass presentation, and a boost in the mid-bass region helped to ensure an engaging, head-bopping sound. For most dance music fans, I guess the true litmus test of a ear/headphone's performance is its ability to get your head moving.
In this regard, I found the V8 more capable than the V6S in depicting the sheer magnificence of a powerful, euphoric EDM track.
For all other genres, I actually preferred the V6S. Classic Eurodance with a lot of vocals, including tracks from Ice MC and Masterboy, sounded better to my ears. These dance tracks were less bass-dependent, and had equal, if not more focus on the vocal reproduction and treble presentation (sparkle, detail, extension).
I guess I'm not really helping by keeping you on the fence, but as a fellow EDM fan, I should advise you on the fundamental difference(s) between the 2. To be honest, if you're going to be listening to EDM tracks most of the time, I don't think you can go wrong with a U8, but if you seek better clarity and an IEM that's more suited for a wider range of music genres, than the V6S (U6) is a better choice.