Well, i'm not picking one I like most. That's not going to happen until i've had either for at least a few years.
The mids on the 650 definitely sound "thicker", but this doesn't mean much to me at all. The mids on the Q701 are addicting and perfect. The HD-650 is just another flavor or headphone to have around.
Despite the 650 being $500 retail, the Q701 is certainly no downgrade. Side-grade. Of course I think two years ago the HD-650 I previously had (bass heavy) was a major downgrade
The 650 I have now sure doesn't sound all that much bassier than the Q701. A tiny bit of more extension perhaps. Doesn't sound bass heavy at all.
Obviously the 650 is much more forgiving of treble/happy harsh songs. Doesn't seem really dark to me, but maybe close.
It's funny to think that I once hated the 650. I actually went out and upgraded my amp just for it and the K702 long ago. If only I had upgraded my DAC for the 650 instead. The K702 seemed to do better with an amp upgrade for whatever reason.
I'm not going to compare these two that much. Just kind of ruins the fun of listening to them.
Of course I do agree that both really need a good desktop amp and DAC to be at their best.
Right now I do prefer this 650 to the 598/580/600. Maybe that'll change in a month
I think I said this, but the Q701 does sound smoother to my ears than the HD-650. Assuming you're listening to very good recordings.