I have the previous version of the Sennheiser - the HD800 (no S) and Focal Elex (a notch below Clear). I have also heard the Utopia, but not the Clear.
The HD800s is supposed to be tuned a little "warmer" than the HD800, so will be a little different than what I describe about the HD800.
The HD800 is more of a "studio" headphone, allowing you to hear everything and some find it leans a little more towards the treble region and doesn't have a lot of bass. The Focal is warmer and will be punchier in the bass.
I think the HD800s are fantastic and they are super comfortable. I also like the Focals, but find them to sound somewhat "artificial". I'm not sure I have the words to explain it exactly, they sound cool, but somehow not as "real" as the HD800s. I suggest you listen to both if you can. They are different animals.
Also pay attention to how they feel on your head. Comfort is a huge consideration, at least for me, when it comes to headphones.