It depends on the title. For Episode I LD vs DVD audio, no contest the LD wins. It is an incredible soundtrack on LD, just like I heard in the theater. For Titanic DTS LD vs the new DVD's DTS, I find them to be very equal, with the DVD maybe having a slight edge in my opinion. In the case of Apollo 13, I have the DTS LD and the new HD-DVD with Dolby Digital Plus. While the HD-DVD is far superior in video, the DTS audio on the laser just kills the HD-DVD. THe Dolby digital plus is weak and puny compared to the DTS laser.

I do think that laserdisc was most often just pretty much the theatrical soundtrack put right on disc, whereas DVD's are now often "modified" for home theater environments. Like a previous poster also said, DD on DVD must be able to play on anything, whereas LD DD was 5.1 only with no downmixing. Whether or not if affects quality is another matter.