I've demo'd both and I can say that unfortunately, you listen to music that crosses divides. The XB1000's have absolutely dominating sub-bass with what I consider to be clear but recessed mids and very recessed highs. The Ultrasone PRO 900s are much more "V" shaped in sound curve, with in-your-face midbass, slightly recessed mids (I find them clearer than XB1000s) and extremely bright highs bordering on the fatiguing when volume is way up.
Dubstep tends to be all about the sub-bass, and only 2 things have ever given me more bass than I can handle when it comes to Dubstep. The XB1000s, and my Super.Fi 5EB's reshelled by Unique Melody. On both of these, the bass literally starts uncomfortably rattling my ear drums before I get the mids where I want them (I have to EQ down the bass). If your end game is sub bass, then the XB1000s *will* be better than the 900s.
For rap, funk, and dance music, I love my PRO900s. the mid-bass common in those genres is just absolutely slamming on my Valhalla amp. The brights actually became much more linear and not nearly as fatiguing after amping, but I think that's because the amount of bass the cans were producing increased.
I love chill-step, rap, funk, and all sorts of Jazz, and for those, the mid-bass effect of the PRO900s makes them my main can. Sometimes, when playing Dubstep I wish I had a pair of XB1000s to use (the XB1000's I used were borrowed from a friend in a trade for a month), as nothing was able to put out such huge amounts of bass with the exception of my IEMs. But for 60% of my music listening, the PRO900s just suit me. The XB1000's would only only be preferred maybe 5-10% of my listening time. If I could have it all I would, and may one day, but now is not the time, so the PRO900s win for me :)
So for what you listed, make percentages of how much you listen to each:
All the others: PRO 900s.
Off hand I would recommend the PRO 900s, but if Dubstep alone is like 80% of your music listening, then you should definitely go with the XB1000s.
You can actually see what I'm saying pretty clearly in the frequency response graphs of the two headphones:
Notice the nearly 20dB difference in sub-bass levels of the XB700's and how that range is so much louder than the rest of the headphone's reproduction area. The XB1000's are very similar (slightly more linear in reproduction).
Edited by rune-san - 9/13/12 at 7:06pm
That may have just been confusing above, but I hope it helped you :)