Just a few theories about how it could be better. If they sample at 192KHz, even on a 96KHz signal, you are still sampling the same level twice. This can give some error detection to reduce jitter, ie if you get a 1 and a 0 for the same level, it can probably be corrected based on the bits around it. If the manufacturer was bold enough, they could interpolate between the two samples to create a more smooth transition. This would allow the use of cheaper and lower order output filters which tend to mangle the phase less than higher output filters required to smooth more jagged or stepped signals. I would think the 192KHz DAC COULD sound better if the manufacturer actually used them and didn't just throw 192KHz DACs on to put it on the spec sheet.