[SoMuchToGrok]

USB is asynchronous - need to introduce timing logic. Optical is by most marks, a cleaner interface.

[otterley]

USB has an isochronous mode, which is used for audio streams. See, e.g., http://www.edn.com/design/consumer/4376143/Fundamentals-of-U...

[mbell]

You still need timing logic, you have to extract the clock signal from the SPDIF signal as well.

[sneak]

It just sounds so much warmer without those few microseconds of jitter, y'know.