yeh but you have zero control over the data stream with spdif, you just get it when you get it. If you start out expecting it to be crap and wanting to dump the clock using a large buffer rather than the typical 1/2 seconds worth of samples you stand a better chnace of having the data you need exactly when you need it. At least that's my experience of the Chord dac and the new hisync usb interface...
Wouldn't mind hearing the Weiss or similar before I take a demo of the Naim DAC, I'm either looking at a new DAc or phonostage before xmas.