Always preferable to avoid converting/adapting protocols
It is very desirable to convert in order to remove timing. Sending music as data and recreating timing on the other side of converter/bridge removes all the noise and timing on computer side. Playback program as well as computer speed don't matter with data transfers. Better yet, slower computer might be better producing less of electrical noise (computer power usage is proportional to speed).
Here is comparison of many USB to S/Pdif converters:
http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/15-universal-serial-bus-industry-standard-cables-connectors-and-communications-protocols-between-computers-and-electronic-devices-spdif-converters-shootout-15327/
Some of converters (tested on DCs Scarlatti and Metrum Octave DACs) matched performance of DCs Scarlatti transport, suggesting that USB bus has nothing to do with it!

