The Bokeh is a more exciting listen if you will, with stronger punch and impact and a tighter sound overall top to bottom, and the Atticus is smoother and more open sounding. The bass is stronger, goes deeper and is more impactful on the Bokeh, but not quite as detailed and nuanced in the middbass as the Atticus. The mids are more even on the Bokeh and I can hear more nuances and little details better as a result. The vocals are different between the two, being more floaty and smooth on the Bokeh, and they are a tad more forward and "raw" sounding on the Atticus. I actually love the vocals on both headphones, and it's tough to pick a winner there. As for the highs, they are more present on the Bokeh, yet still don't ever get harsh. I feel overall the Bokeh has better balance and extension top to bottom, and more unique staging and better layering thanks to the ADS (Atrium Damping System), and the Atticus is more open and "flavored" with more peaks and valley's in it's FR and it sounds more laidback overall. That's just some off the cuff stuff of what has really jumped out so far, and I have only had 2 weeks with the Bokeh now, so I am still learning what it's all about and how it fully compares to my Atticus. That being said, I already know the Atticus and Bokeh are different enough that both are staying in my collection. The Bokeh is more balanced/analog and dynamic/punchy sounding, and the Atticus is more flavored sounding with it's peaks and valleys, and more laid-back/open sound overall. I can listen to either one happily all day long.
For reference, the Bokeh has the Hybrid Pads and Titan Mesh installed, and the Atticus has the stock Ori Lambskin Pads.
I truly feel that if you are a fan of the ZMF house sound, the Bokeh is definitely a must have.