I think every discussion ends as soon as someone says he just plain enjoys a certain headphone. Why shouldn't he? Enjoying one's music is all one can ask for. If Neruda and Xander enjoy their K 401s - why not? No one could tell them they shouldn't.
It's just that I have never liked those AKGs. Or Senns. And convincing someone of the merits of the Beyer 770 Pros isn't exactly easy. Maybe that is the reason I try to compensate for the lack of manpower at Team Beyer with loudness.
This muddiness vs. airiness controversy is quite intriguing. When I listened to the closed 770 Pros, I had a similar impression at first. The 990 Pros, that I knew pretty well by then, seemed "airier", more "spacious". Their soundstage seemed simply larger to me. But at the same time, I realized that I enjoyed the 770 Pros more. I perceived them to be even smoother and more engaging. And warmer. And this compared with a headphone that is probably warmer than most any other higher-price headphone out there (well, the Beyer 250 has similar tonal balance). Now that I am very familiar with both the 770 and the 990, I have realized that this "airiness" of the soundstage is somewhat artificial. That the added detail is indeed added and does nothing to better convey music. The 770s are even more natural and have a more believable and deeper soundstage. And as I have said above, they have better dynamic coherence. And to me, it is their very homgenousness that doesn't let them get in the way of the music. I think, it is indeed their natural warmth, that lets them sound more transparent.
I feel that most headphones sound rather thin, that they have far too prominent treble and that this screws up their timing, their transparency and their ability to involve the listener. Considering the fact that most highly regarded headphones have a brighter tonal balance than the professional Beyers and try to provide "detail", and that it's detail, many of us are after, my preferences must seem rather extreme, I guess. But that's how I hear it.