Squeezebox duet best sounding output?

Would it be better to use the digital RCA output or the optical output to feed a outboard DAC?
Bedroom system: Quad 12L,Cambridge 640A integrated,vonschweikert vrs1 sub,Music Hall dac 25.2

Thanks for your thoughts
I tried both coax and Toslink from Duet feeding DacMagic. I prefered the coax. Seemed to be smoother, with more defined bass.
Why not try both and decide for yourself,after all,you are the one that will be listening to it.
I just purchased the DAC, it has not arrived yet. I am looking to spend up to a couple hundred for a decent cable. Buying both a toslink and a digital would cause domestic unrest. I need to pick one and live with it for a while. Thanks for the responses