Optimal transient here too. I have used the Optical Spectrum and though I can't hear any difference I do tend to find that the Optical Spectrum is more tiring to listen to; it's harder on the ears.
I think that the manual says that the differences are subtle but I'm damned if I can hear any differences. The manual doesn't help a great deal in explaining what the differences are between the filters with descriptions in somewhat technical terms.
I have to say notwithstanding all that, I do love how the 8200CD makes music sound and it's flexibility.