-- Why is Ethernet superior to USB? answer: both are asynchronous and therefore should be the same. But USB needs to be galvanically isolated to prevent noise propagation. Also, see above, network allows you to remote the whole thing and eliminate physical/mechanical noise
Ethernet is superior the USB because there are fewer hoops to jump through and less money to spend to acheive audio nirvana. They can both be identical in SQ, but USB takes a lot more and requires a really good computer and power supply and USB ports/USB regenerator/USB cable/kill the background apps/select the right playback software and even then you are usually stuck with a substandard USB interface on your DAC. No thanks.
I have my own stellar USB converter/interface that matches the performance of my Ethernet, but it's a lot more trouble. Handy for Amazon Prime music and listening to sample tracks from Amazon though.
Steve N.