Nightflier, the only thing I have to say about the audio on these two formats is that Mr. Bungle from PeeWee Herman was at work on the audio design of these machines.
I think that Dolby True-HD has some relationship with DVD-Audio. BD can output the PCM tracks that are on many BD discs at least through analog outputs if that machine has them. I think that track might also be outputted with HDMI 1.2 into a receiver. I have not read any articles talking about SACD and BD-HD-DVD machines and a realtionship there at this time.