I have the 600's and the 650's, and have had the 701's and 595's and 580's.
I agree, the 595's and 650's do not have the admittedly very, very slight glare of the 580's/600's.
That glare, for lack of a better descriptive term (grain?), can be slightly fatiguing.
I don't think it's possible to become fatigued by the 595's or 650's (for better or for worse!).
Now, the 701's - - -
They are a VERY good headphone, just not for me. My complaint is that they are a tad "thin" sounding, without a rich harmonic structure. Again, I have no clue if I'm using the right words here. But you get the drift.
The 701's are, though, very clear and detailed.
I did NOT ever find them fatiguing from brightness, though. I was expecting that, and was quite impressed that they didn't tire me. They are a very refined headphone, more so than even the 600's.