The difference on this one between DTS and Dolby appears to be simply a matter of adjusting the volume knob up or down on your AVR.
Audio hobbyists need to take to heart the psychoacoustic fact: simply 'turning it up' (or down) can account for a multitude of 'OMG X IS SO MUCH BETTER THAN Y" impressions.
It's a bit more than that. It's a balance issue. You have to turn the volume up on the rears of the DTS, and to different levels for different songs. Not the case on the DD. Very strange situation.
But, as you say, it has nothing to do with the encoding system. Purely levels.