I briefly owned both at the same time before I sold the Atticus. In my opinion, if you can afford both and you like EDM, rock, or hip-hop, then yes own/keep the Atticus. Because those are the genres where the Atty really shines, and in some occasions may even be preferred over the VC. But the VC is hands-down better overall on all music and is a much better "investment" in terms of value and usefulness. It may just come down to your mood. If you enjoy jazz, acoustic, pop, and live vocals more than heavily-processed or compressed music, then you will be much happier with the VC because it's a superstar in tonality, detail, and soundstage. It's amazing on the heavy stuff too, but it doesn't enhance the midbass the way the Atticus does. But don't mistake the VC as bass-light either because it actually plays lower frequencies than the Atticus with more authority. It's really hard to fault the VC on anything and the Atticus does really well where it shines best. From 60-120Hz the Atty will have your head knockin' like no other. The VC has the capability to rattle your teeth from 20-40Hz (amplification dependent), massage your temples from 200-800Hz, and tickle your nose hairs at 12k-16kHz all at the same time.
Sooo bottom line, yes there is a reason to own both headphones, and if you can (or just want to), then do it! But many (and most in this thread) will tell you to just save up twice as much and get the VC .
Really good synopsis. I also found that the VC being larger than the Atticus, made it a more comfortable headphone. Although perhaps that was just a difference in pads and my big ears. The Atticus is by no means uncomfortable.