I mean compared to AKG Q701 and Beyer DT800 (600ohm) Senns have blurry bass, I was driving them with O2 or Magni with Modi DAC. However both Bayer and AKG have their issues. Besides uncomfortable headband (can be fixed) and famous 2K spike of Q701 (which could be solved by eqing) I believe Q701 is one of most clear sounding headphone on the market today (below $500). DT880 have more bass but resolution and separation Q701 have is no-brainer. Unfortunately Q701 also have less bass among all above mentioned competitors.
Generally every headphone have some flaw, especially open back headphones have more significant flaws, considering this I would choose Q701 if I am about to buy open back and save money. Besides tonal balance HD600 is winner, I would like to hear good resolution and separation which they lacking. Cured Q701 can provide both.
Also asking price $399 for HD600 is a blatant robbery hence better save some money
Cheers
P.S. I had all of them together and compared side by side for months.