Dolby tends to use dialnorm and DTS does not so the volume levels are different, having said that try this, Put in the DTS version of SPEED and compare the music soundtrack to the Dolby version. The intricate nuances of Mark Mancinas' percussion instruments are a blur on the DD track, whereas the DTS track reproduces these subtle shadings with improved clarity, soundstaging and pinpoint instrument placement.
This is a consistent quality I find inherent with DTS. Music always reveals the superior SQ of DTS vs. DD (( Speed DTS Region 1: CH 5 12:07 after they kick the door open, listen to percussion elements of the music. In DTS it's very detailed, on the DD track, blurry))
Many Quote the DTS version of Saving Private Ryan or indeed the DTS version of The Haunting but both used completely different masters thus you cannot compare the 2 different codecs on these particular films, the same is true of the DTS version of Dances With Wolves it uses a different master for its source as does the DTS version of Criterions The Rock.
I believe i read somewhere that the compression rate isn't the only factor, isnt Dolby working at a 36millisecond delay factor where DTS uses 10millisecond delay for its codec, take that into account and it shows that Dolby is more efficient at lower bitrates and DTS needs higher bitrates just to keep the same level of sound quality, basically Dolby at 754 kb/s would blow DTS at the same bitrate out of the water, when Hd-DVD gets released Dolby will probably use 640kb/s for DVD and most titles will sound superior to DTS if halfbitrate is used, probably identical if Fullbitrate is used unless a different master is used for the DTS film titles and thats where the differences in sound are heard. if the same master is used then calibrate your systems and that includes the surround channels and usually there is no difference.
I for one hope the next generation of DVD will bring a superior sound format to the home and hopefully MLP will be the chosen sound format.