Going USB to SPDIF should give you better performance because it the USB part is buffered and thus, in theory, jitter free. You also have the advantage of being able to run a long USB line if needed from the Mac to the receiver.
The HagUSB is an excellent USB to SPDIF converter if you don't need any extras. Comes in kit or ready built form.
The HagUSB is an excellent USB to SPDIF converter if you don't need any extras. Comes in kit or ready built form.