I used Bricasti M3 network card connected with high quality Ethernet cables for a while until I tried Aurender N200 via USB into the M3. Blew away using the network card.
Internally, the M3 network card is connected to the board using I2S if I am not mistaken. In general, I2S was developed for internal connections and that is partly the reason why there’s no industry standard for thr pin configuration which in some units makes it a crapshoot selection a transport for it. Whether or not it’s the best connection is debatable. Fo me the USB out of N200 into M3 was in another league.
So…when making blanket statements about what connection is best sounding you only show your lack of consideration and understanding of what the best connection on a given component is, out or in, for a particular listener, and why that is the case. Equipment compatibility and synergy is key. Especially for I2S that has more pin confirmations than California has raisins. Good luck to you.