Ok, I got the Clear MG Pro in, and I've been listening and comparing to the original Clear for an hour or two.
Here are my first impressions:
It is indeed warmer than the regular Clear, as many have already said (which is exactly what I wanted!). There's more of a rise starting from the upper bass all the way down, it has a similar mid bass hump of the HD650 or 600, maybe not as elevated though. You can feel the impact a bit better with the MG compared to the OG Clear. The bass is just as clean however, it does not bleed into the lower mids, as far as I can tell. It is just slightly fuller and warmer. Also, it might be my imagination, but the bass might be slightly more responsive. Perhaps that is a result of the sub bass extending better.
The mids are about the same level, vocals are very nice and present. The original Clear sometimes sounded strident with certain tracks, and I don't think I hear that with the MG Clear. It is very smooth, yet has the same dynamics you would expect from a Focal headphone.
The treble is the most notable difference to me, and for the better. With the original Clear, there was always a narrow treble resonance around 10kHz that even when equalized, you could still hear some traces of it with the right recordings. I am happy to report that Focal has improved the treble to the point I can listen to the MG Clear without EQ, and it still sounds fantastic. There is still a slight rise at 10.5 kHz, but they mostly got rid of that resonance, and they also lowered the level at 6kHz. In direct comparison, the OG Clear sounds more strident and peaky, while the MG is much closer to the tonality I am looking for. It is especially noticeable with recordings that have cymbals and high hats. You can hear the occasional peakiness and splashiness with the OG Clear, while the Clear MG sounds quite a bit smoother and more natural to me.
Overall, the MG is even closer to the tonality of my HD58X than the original Clear. That's a huge win in my book.
My impressions will probably change, but it's looking really good for the Clear MG! I think it boils down to whether you prefer a more analytical flat sound, which would be the original Clear, or if you prefer a warmer smoother sound, the Clear MG. In my case, I prefer the MG.