Thanks for these impressions!
Can I ask if your Solaris has been burned in much?
I've currently got one burning in prior to starting my review process; my impression out of the box was that there was significant mid-bass presence, definitely going into 'bloat' territory.
It’s a new review unit. Personally, I've never heard any audible differences on my IEMs, but I’ll probably give this one at least ~100hrs. It can’t hurt, and I have seen quite a few comments about that! I don't have the patience (or time) for ~500hrs though, haha.
I haven't heard the 2020 but relative to the OG/SE this is almost comically untrue. The u12t has very nice bass for a BA with a nice natural decay. However relative to the bass on the Solaris (SE/OG) the u12t's bass is almost thin and wispy by comparison and it lacks the density and subterranean definition, nuance and extension that the Solaris has. Again, I can only speak to the OG/SE but I find it hard to believe that the situation is different in the 2020.
Can only comment on the 2020 unfortunately. One of the key distinctions between a BA/DD (for me at least) is texture. I find that BA's generally decay too quickly to produce this, and the Solaris 2020 is eerily reminiscent of it despite having a slower decay. Really not sure what to make of it. I certainly hear more dynamic slam and presence, but the texture...just isn't there. Both the U12t and Solaris 2020 extend nicely to my ears.
The Solaris strikes a nice balance of providing excellent layering and detail retrieval without losing sight of presenting the music as a cohesive whole. The u12t is a great IEM if you want to listen to details but (imho) the Solaris has the edge (as does the Andromeda) if you want to listen to music. Honestly this is undoubtedly some people's thing but I found the u12t way too clinical to hold my attention and interest in the long term.
Yeah man, I'm very much aware that this is why you (and many others) like the Solaris! I totally get what you're saying, and I subjectively enjoy listening to the Solaris myself. But like you noted, I have a predilection for more balanced, resolving sound signatures. It's what keeps me listening in the long run. I prefer the Andro 2020 over the Solaris 2020 by a good margin, as well, because I find it has a more "laidback" quality to it like the U12t.
How about against the Nio?
Should have a review unit for that coming in soon