Oh dear, here we are again. Head-fi is turning into quite the broken record lately. Here is something to think about, audio USB does not have error correction, simple fact in most cases of usb implementation on the dac side. Second, timing issues are possible in usb cables, dielectric absorption and dispersion as well as conductor dielectric velocity mismatch, this is called jitter. Third, shielding can make cables sound different from one another, this is obvious. Fourth, a lot of people seem to make the mistake that it is the 1 or 0 that is being read and turned into the analog wave, the problem is when the dac must round (incomplete voltage swing). If the dac gets say +.51 volts then it may round up, what about .49, .409. 499 etc. etc. these can cause the bit to be misread. Then the bits are only representing points in the magnitude and frequency of a compound waveform which can have infinite variation because it is an analog wave (think any two numbers have infinite numbers between them).
There is plenty of room for variation in usb audio cables. Whether or not the differences are audible is the real debate.
Dave