I would add that, to my surprise, the 2020 XC also out resolves the Arya. Since that is a very nebulous claim, I'll provide a concrete example.
On "Hey" by Pixies off of Doolittle, there is an very faint trace of the vocals track that runs in the background of the song. It's right at the very start. Black Francis starts by shouting "hey," which should then be followed by progressively fainter "hey, hey, hey" as a sort of echo. Next there is a bass note plucked immediately followed by a very faint "been tryin'" before he returns to sing "been tryin' to meet you" at normal volume. This is one of my standard test tracks because not everything resolves those background vocals at all, let alone well.
On the Arya, I can hear two of those echoey "hey"'s and just the merest presence of "been tryin'" without actually being able to make out the words. On the XC, I can distinctly hear all three "hey"'s and "been tryin'" in the background. I volume-matched, of course, but the kicker is that turning up the volume on the Arya to 90db and turning down the volume on the XC to 80db yields exactly the same results, which suggests that this is not merely an product of the different tunings of the headphones giving the XC more presence in that particular frequency range. In this case at least, the XC just pulls outs more detail.
I had thought the Arya would be the one to dethrone the XC, but it looks like that's not going to happen. Audeze really has created an amazing headphone here!