Blu Ray (BD): Dolby True HD/DTS HD from HDMI vs Standart DTS from SPDIF (Core-Stream)

Blu Ray (BD): Dolby True HD/DTS HD from HDMI vs Standart DTS from S/P-DIF/DOBM (Core-Stream):

I want to know about impressions concerning sound quality between this two kinds of sound reproduction:

1) old S/P-DIF multichannel top class decoder
vs
2) newest HD multichannel top class decoder with HDMI input

with the same Blu-Ray Disc (BD) player model.

Thank you for sending your impressions - I need this informations for a friend; who use an older 5.1 decoder model (Mcromeda Minimum or Minium) and will buy now a BD-player. He would like to know, how large is the disadvantage concerning sound in opposite to a decoder from newest generation.
 
On the paper there is a big difference. In realty there is none between DTS (Core) and newer formats. The movies don't have sound at the quality level that would require the upgrade from regular DTS. As for music, there are just a couple music bluray discs released. Dolby True HD has the same quality as DVD-Audio (same encoding format). DTS HD is at the same level.
Personally, for music prefer SACD.
 
Nope. In reality, Toslink introduces a 2-second silence at the start of a surround sound for some reason I don't understand; HDMI doesn't have this oddity. Don't be fooled by the fancy optical labelling; HDMI is built for this use. But theoretically, they have audio differences check here (S/PDIF) vs HDMI vs Analog explained.