Still early impressions, and not entirely equal in that the A2 is running Unison USB and the A1 is running I believe Gen 3 USB (shows up as a "speaker" when connected).
I have an Eitr arriving later this week to play around with as well.
Also thinking of updating the USB to Unison on the A1, not sure yet, but getting the warranty extended by 2 years in the process ain't half bad.
My source is Qobuz (macOS) --> USB --> both Gungnirs
The A1 is notably warmer along with what I perceive as a fuller/deeper stage, and a bit more bass emphasis.
It is however less present/detailed/clean on the top end than the A2.
Could any of this be due to the differences in USB implementation ... sure, maybe, no idea.
The FV has 2x RCA inputs which is where I've been doing most of my comparisons from.
The MJ3 inputs are 1x XLR and 1x RCA which makes things a bit less equal.
At the end of the day one of them is going to stay with the FV and MJ3 (work setup) and the other is going into a second headphone rig feeding an MJ2 and Valhalla 2 (home setup) - I haven't told the Bifrost in the home rig this yet though ... more personal Thunderdomes to come!