I had to yank the BF2 from the bedroom setup but spent the day listening using the SE outs through the Freya S and Vidar. With the universal caveat that listening is so individually subjective, here’s my impression: Both are wonderful DACs but I have to say there is no beating Yggy. The biggest difference is the width and breadth of the soundstage, better three-dimensional imaging of the instruments, subtlety of attack and decay. The Bifrost had a more forward presentation.
Is Yggdrasil worth the price difference? Could I quantify it to be $1,750 better? I think such comparisons are impossible to do. That said, Yggdrasil is better, whether you use SE or balanced, and by the end of the day I missed it. All that said, I still find it remarkable that BF2 is so good at the price, and in a remarkably compact size. Yggy is large and that always has to be a consideration, though for two channel setups that’s usually not as much of an issue.