My recent search for headphones ended with a short list of two - the Senn HD800 and the Beyerdynamic T1. Both are outstanding headphones in their own right, but to me the difference between them came down to their musicality.
I found the HD800 to be more analytical - I found myself listening to recordings and being impressed with how good a recording sounded. With the T1's I found myself getting drawn into the musiccal experience and lost in the music. I have not regretted buying the T1.
If you are looking at high-end Senns or Grado, you owe it to yourself to compare them to the Beyerdynamic T1 as well.
I found the HD800 to be more analytical - I found myself listening to recordings and being impressed with how good a recording sounded. With the T1's I found myself getting drawn into the musiccal experience and lost in the music. I have not regretted buying the T1.
If you are looking at high-end Senns or Grado, you owe it to yourself to compare them to the Beyerdynamic T1 as well.