Do you get more of the emotional connection from your HD650's? If so I can definitely understand. I go back and forth between the 700 and 650 constantly.
I do and I suspect there's something in the FR curve that would explain why that is, with my playback chain, but I wouldn't be able to articulate the reason.
It may be the amount of time I've spent with the 650s, relative to the 700s ... don't know. I am trying to spend more time with the 700s to see if that's it. But I was listening to the new Florence + the Machine album the other night with the 700s and felt like something was missing; switched to the 650s and went... aaahhhh... nice!
I think the reason for this might be that the HD-700's sound stage is too wide for some genre of music to sound natural. I also noticed that I like the HD-700 better on the Ember (hydrid) vs the BH Crack (OTL) due to the adjustable output resistance/impedance, where the BH Crack is geared specifically high impedance headphones like the HD-600/650/800 and Beyers. If listening to classic rock the HD-700 sounds un-natural to me due to the sound stage being to wide, but the bass is nice a tight, goes low, mids are a little recessed to me, highs have a nice shimmer, on the HD-650 the bass is not as low or tight, the mids are slightly forward and the highs don't have the shimmer of the HD-700 but are not a problem and the sound makes me feel like I'm right in them middle of the studio. For classical the HD-700 is way ahead of the HD-650, the HD-650 sound constricted and the dynamics sound compressed to me.