I go into some detail here about what the different surround formats are, which may be useful.

Which is better is a matter of some debate. Many people feel that DTS is always superior, while many others feel that the fact that DTS is typically mastered about 4dB louder than Dolby Digital (people often equate "louder" to "better sounding"). I've always found the differences to be fairly small - possibly because I always tweak my volume level "to taste" while watching (thus equalizing volume between the different formats).

If you didn't get anything at all with DTS, your DVD player is probably set to output DTS as PCM. This is a common default setting that should probably never have been defined that way, and should certainly have been adjusted many years ago. You must have your player set to output DTS as either "bitstream" or "raw" to get the original signal from the disc.