unfortunately i haven't a link to listening tests - my conclusions are based on technical characteristics of both codecs and some informal testing on my own part (through headphones only - certainly wouldn't be acceptible on hydrogenaudio
).
all things being equal, the ac3 will
probably sound better, and will certainly have higher bandwidth, especially when compared to DTS at 754.05 kbps. i'm talking about ac3 at 448kbps here btw...
however, all things are not equal. usually the DTS track is produced from an entirely different master - in here we often get in a "5.1 mix" tape, and a "5.1 DTS mix" tape. the dynamics are different, usually the bass is overblown in the ac3 mix. this isn't due to the codecs - just the way the mastering engineers have made 2 different mixes. it's funny - when people hear a difference, it's mostly because they're hearing different sound, not because they're hearing different codecs (there's a bit of that too i suppose).
one of these days it'd be cool to do a test encode of ac3 and DTS off the same tape, however i can't see myself doing that as i've got a new job and am only here for a few more days (hooray for me).