Let me be perfectly clear.... Jitter doesn't matter with the Cherry DAC DAC! The DAC DAC re-clocks the data internally, and jitter tests show no effect on performance unless the jitter is so obscenely bad (doesn't happen in real life) that the interface itself doesn't work.
Yes, optical does provide electrical isolation, but for devices like the Cherry USB, the output is electrically isolated anyway (internally), so there's no benefit to optical there.
Also, optical is more common in certain applications, like the HDMI ARC (Audio Return Channel) on TV sets. We use COAX for SPDIF because it's reliable and uses a common cable type.
The DAC3 will have an optional optical input and a selector switch to select COAX/OPT on the back. Thanks.