Nice write up. I also started doing some A/B comparison today as reached the 300 hour burn in. For context, I found the Semper to be a bit too clinical and I sold them in favour of the Elysiums, which were more fun for my taste, so comparing the Avalon with the Elsyium.
It's an interesting comparison and not as cut and dry as I was expecting. The Avalon sounds amazing, no doubt about it. In almost every way they are better than the Elysium and on paper are the best IEM I have ever listened to. I was expecting to compare them and sell the one that came off less favourably but I don't think it's going to be that straightforward.
I hadn't realised until this side by side comparison how much the Elysium really 'glues' bass and drums together. Avalon has a better and more detailed overall presentation and is no slouch in that department, drums hit hard and sound amazing, but it doesn't groove quite like the Elysium does... I can listen to a song on the Avalon and think 'that sounds amazing' and not feel like I'm missing out on something but then I put the same song on through Elysium and it's a bit more visceral and my head is bobbing immediately in a way that the Avalon doesn't. Possibly the natural result of having a wider soundstage and better overall separation, you don't quite get the same focused attack / transient response through the middle to really get things moving in the same way maybe?
My Elysium have had roughly 100 hours more time on them but I'm not sure that any further burn in with the Avalon will close the gap in this particular regard, I think it's just their signature but YMMV as they say. If there was some way of achieving the best of both of these worlds in one IEM that would really be something.