AFAIK, both are theatrical mixes. DTS was “remuxed” in 5.1 by Schorman directly from the theatrical DTS CD-ROM, while LD Dolby 6.1 was directly taken from the theatrical Dolby track.
So IMHO, both deserve the name of “cinema”, and Chewie’s question (which audio will be defaut) is a difficult one…
BTW, does someone know if the theatrical SDDS track can be found somewhere ?