I have owned both for a couple years now, and first off they are both fantastic headphones. Also, just for reference my Atticus is in Cocobolo (a harder wood than stock), and my VC's are in Ambrosia Maple (lighter wood). The Atticus is warmer, thicker and more mid focused with a smooth and powerful sound, and the VC's are faster and tighter making them more nimble with a more "neutral" sound. The VC has better extension in the sub bass and treble, and have a more linear sound top to bottom that works well for any genre I throw at them. My Atticus are more of a specialist in that they are more mid focused, with the big focus on the middbass and then another little peak somewhere in the upper mids, that helps balance out the middbass. The VC's have a bit lighter touch, and are much more open sounding, and the Atticus are heavy handed and smooth with more intimate staging. Both headphones are warm, but the VC's speed helps all the detail come through better. I like my VC's for every genre, and my Atticus for anything guitar focused and acoustic stuff. One last thing, the Atticus is a more forgiving headphone that I can listen with loud and long, and the VC's will let you know if the recording is bad.
Hope that helps a bit.