Having never owned a Mojo 1, I first bought the Mojo 2, then the Hugo 2 and then the 2go, I can give you some perspective:
The Mojo 2 was intended as an upgrade from the Shanling M6 (AKM based original) that I was using. I'd bought the Quad ERA-1 headphones and while the Quad / Shanling combination showed excellent resolution and detail, it lacked a bit of dynamic punch as a combination, the ERA-1 being a low impedance planar magnetic and the M6 being better suited to efficient IEMs. The Mojo 2 with it's nearly 4x output power seemed like a good idea, with many reviewers raving about the Mojo 2's resolution, I was expecting to be blown away. The reality was, to say the least, unexpected. Drive, dynamics, scale and sense of rhythmic integrity were definitely a big step up from the Shanling M6 using the Mojo 2 / ERA-1 combination. There was also this lovely "fluidity" about the delivery, a sense of detail and pace without being forced, free of strain or effort. However, there was a price to pay. Bass was more present, but less detailed. Subtle amplitude changes and texture seemed to have gone missing. Overlapping similar frequency events in the bass seemed more homogenized. Further up the frequency range, there were similar losses where fine amplitude changes were needed to created the detail in filigree sounds. Some rendering of relatively quiet metallic textures sometimes seemed veiled. The differences were not huge, needing much blind A/B listening to work out specifically what was different, but I couldn't live with the loss of finesse. Overall, it was very similar to the Shanling M6 sonically and with simpler music, it would need careful listening to work out which was being listened to. The M2 was retuned (it also had white noise episodes). The big benefit of the M2 was the EQ, adding +2db to the 20Hz region giving a weight to the bottom end that I'd describe as perfect for the ERA-1.
Next step, try a Hugo 2. I bought a demo model to try out with the intention of spending a week using every spare minute to carefully evaluate areas where it might improve on the Shanling or the M2. The reality was again unexpected. Where the M2 had failed to blow me away, the Hugo2 Quad ERA-1 pairing really did deliver a punch in the face, blatantly obvious set of improvements. Less than a minute of listening was all that was needed to hear this, the improvements needing no detailed A/B listening to detect. The Hugo 2 was hugely more revealing of the subtleties and nuances that the Shanling had been partially portraying and adding a big step in detail and transparency well beyond anything the Shanling M6 or Mojo 2 could portray. Combined with an improved sense of drive, pace and dynamics, this one was definitely a keeper. Even better, when I took the demo unit back and bought the new Hugo 2, I bought a 2go as well. Getting the pair home and discovering that the 2go moves the sound up a bit further was a pleasant surprise!
So M2 vs H2 is not really a fair comparison and the performance difference does reflect their respective price points. Does the M2 get close? Well, yes, in some ways, but the Shanling M6 gets a little bit closer in many respects. That M2 EQ is a very nice touch though. I wonder if an H3 is on the way with similar EQ capability. I'd buy that.
