I bought one of these recently. IMO, its a major upgrade over the 70D, which I bought, ran, and sold in a span of 48 hours.
That said, I did a Comp last night between the 701D and the MixPre-6. Absolutely stunned by the results.
Besides its excellent sound quality, here are my likes when comparing the two:
1) I can run it with a small pocket-sized Anker battery. In this case, the Powercore 13000. Last night's record time was 4 hours 58 minutes, P48 on, and still had half-a-battery left. WOW!
2) No polywav file nonsense
3) I can turn off the Mix so it won't record the Mix files.
4) One, big, scroll down menu. Makes setup quicker.
5) It has a "Hold" button
The 701D's sound quality is every bit as good as the MixPre-6's.