Interesting, haven't heard the Q701's but I found the K712s much smoother and better balanced than my stock K701s and were very similar to my HD580/600 but with more extension and body in the bass.
I found the K712 smoother but it's dynamics are stronger thus why it's a bit more aggressive to my ears, I found the Q701 brighter and not quite as smooth, it also doesn't quite have the depth, body, imaging, and transparency of the K712, this is with pad swapping. The soundstage came off as flat and overly wide on the Q701 compared to the K712. To me the K712 sounds nothing like my HD 600, relatively similar tonal balance but that's where the similarities end for me.