To me the 700's are to bright to the point of being fatiguing. The 650's are missing some treble. For me it's either the 600's or the 800's.
I spent an hour carefully comparing all four. I went in expecting to get the 650's, willing to stretch the budget to the 700's but ended up leaving with the 600's in hand but staring at the 800's with wanting eyes. Since then I picked up a pair of HE-500's and am very happy with them as well.
Who IS this guy??? Always has the RIGHT answer!!
Sorry, wrong. (tongue-in-cheek)
The HE500 certainly is clearer if you are listening to faster and more complex passages, its a faster headphone and resolves these passages more distinctly and with better separation. Its imaging on my system is superior. Both of these things make me say it has better clarity. I view detail in the realms of how easily you can hear things like background noise in live recordings, distant effects in ambient electronic and things like that. Treble tilt is not what I'm talking about when I mean detail at all. Neither of the two headphones would that detailed by that criteria.
Obviously, everyone has different opinions, and I've made mine known.
When I owned the 600 and 650 side by side, I couldn't wait to get rid of the 650; just too much stuff missing from the upper end, and the lower end was too emphasized (colored).
I love the HD600 for what it is, but I believe the HE500 is definitely crisper and on a higher tier. It is "my HD650", in that it's the go-to headphone to mellow out, or listen to lower bitrate or poorly mastered material, but much more balanced and resolving (yes, I know, resolving doesn't mean anything). The HD600 will always be a timeless classic.
All the usual disclaimers apply (IMO, YMMV, etc)