I have all 4 massdrop made: Fostex ebony, Senn 6xx, K7xx and Hifiman, By far the super standout is the Fostex - 90% of the population would agree its the best headphone they ever heard.
I own both the K7XX and Ebony TH-X00.
TH-X00 Ebony are great all around "semi" closed phones. If you play loud and don't want your sound going out or your environment noises getting in, look elsewhere. They aren't "open", but they are vented. I tried using them in my cube at work and they vent too much. Back to my trusty closed Beyer DT770 for work use.
The TH-X00 do sound amazing though. Full, broad audio representation.
K7XX cost under half. So I feel they perform WAY above their cost. Very light and comfortable for long wear. They are totally open, so take that into consideration for your listening environment. I use them at home when I'm alone and don't have to be concerned with bothering others.
They are apples to oranges and fill different goals.
The TH-X00 are great HPs.
What idiot put the Grace DAC/amo in a "which headphone" poll?
I know they are an idiot because they couldn't even get the price right.
These polls need some kind of moderating.
Kind of comparing apples and oranges. Open-back vs. closed back, plastic vs. wood and metal, and one is 2x the price of the other. I have K7xx and its open back is great for singling out instruments and getting a feeling of space, but the plastic and headstrap is very fragile, which is nice for weight but I'd never go on a trip with them. I'd imagine the fostex is built like a tank in comparison, but I like open-back a lot more than closed-back, especially for acoustic and classical music.
I've given both much listening time and the TH-X00 is better in every way, significantly. Except the K7 is open.
No matter the music, I like the X00 better.