Sennheiser or Beyerdynamic?

Max budget $600, non-wireless, open back. I own a Benchmark DAC combo-headphone amp. Comfort important, but sound is more important. 

I’ve heard good things about BD’s Amiron home model. Also the Senn’s HD660. Anyone done an A/B shootout or own both?  I’m into hi rez digital and DSD music of all kinds... mostly pop/rock/folk/vocals and natural recordings of acoustic string instruments. Also Jazz and Classical.