I've got both and am happy to have them both in my collection.
The Andromeda 2020 has a darker sound signature than the original Solaris. This means that, for me, it makes for a different listening experience: it's more forgiving of poorly recorded genres and it's less fatiguing (not that the Solaris is fatiguing). I love it for alternative rock. The darker tuning makes the Andro 2020 more of a specialist IEM for me than the Solaris. The Solaris works with all genres; the Andromeda 2020, less so. The Andromeda 2020 also has certain timbral and textural qualities that I really like; i some way, I prefer the mids of the Andromeda 2020. The Andromeda 2020 also has a slight mid-bass emphasis, which again makes for a nice bit of texture with bass guitars and double basses, but the Solaris has a deeper sub-bass extension. The Solaris also has a better, smoother treble extension - for my tastes - and it provides the kind of sparkle that the original Andromeda had but that the Andromeda 2020 lacks, given its darker tuning.
All this is to say that while they share some similarities - a nice, light touch to the sound, excellent resolution (the Solaris is slightly better here, I suspect), excellent speed, and lovely open and spacious staging - there's enough to differentiate them that, for my taste, it's worth having both. They also play well off the same sources when it comes to hiss and to matching the output impedance to suit your preferences (e.g. lower than 1 ohm Z out for darker, bassier tunings). I hope this helps!