I've tried my friend's HD700 for a week on the Magni 2/Modi 2 Uber stack I had at the time. I was playing CD quality or better lossless and DSD.
From what I heard, the 700 has very nice detail especially in the treble. The highs can get a little tiring when listening for a while. What I found odd about the treble on the 700 is that it's much brighter than the other headphones in its line. Where Sennheiser is typically known for slightly rolled off highs (some people call it the 'veil') the 700 goes the opposite direction and provides an unusually sharp/crisp/pronounced top end.
The bass is typical of Sennheiser, where it has good definition but is definitely not overpowering. Compared to my HD650, the bass is less in quantity but tighter and better defined. This makes the headphone great for classical and jazz but not very good for pop or electronic.
The mids were decent, but obviously not the star of the show.
Overall, I didn't quite enjoy the 700. Those cans work best for classical, acoustic, and jazz but almost everything else didn't sound appealing to me through these headphones. The treble got a bit sharp at times and became tiring to listen to. The bass, although tight and fast, was a bit light for my tastes. I found myself analyzing the music and trying to pick out details, instead of enjoying it. That is, more or less, what you buy the 700 for - analyzing. If you enjoy listening to music so that you can hear every detail and focus on them, then this may be for you. But I personally find the sound a bit boring and cold. It was very hard for me to put these on and enjoy the music I was listening to.
I hope this helps you understand the 700, at least from my point of view! I've done my research on plenty of headphones and I will say that my opinion here does match up with plenty of big reviewers online.
I can't speak for the Hifiman but if I were the one choosing, I would pick the HE560. Perhaps if it were between the HD800 and the HE560 my choice would differ, but I would have to find some ridiculous discount on the 700 to ever bother purchasing them for myself. Good luck with your decision!