Hi David,
I think the difference between USB and Ethernet connections is a little bit overstated sometimes. Neither was designed for audio but both have actually morphed into very useful ways to transport digital music.
They are similar in that both come from the computer world. USB as a more-or-less ubiquitous standard from the PC world, enabling DACs to be connected to PCs and subsequently being adopted by many streamer/server manufacturers, and Ethernet as the universal standard for local area networks. Both are asynchronous, which is a huge advantage as it eliminates jitter concerns, and both offer sufficient bandwidth to support high resolution 2 channel audio and more.
The main differences from our perspective are that Ethernet is galvanically isolated by design, which USB isn’t. However since this is something we regard as quite important we have isolated the USB interface in our products inside the units themselves. Also, Isochronous USB (the variant used for audio) lacks guaranteed delivery, erroneous packets are not retransmitted, simply discarded, although I doubt this makes any major difference in properly engineered implementations.
I personally prefer Ethernet as it is the “lingua franca” that everything in my digital audio chain speaks (my Roon Server, UPnP server, NAS, and all my network DACs) so “everything can speak to everything” which is really convenient.
But in dCS implementations at least there shouldn’t be any significant difference in SQ.