Which audio

Hi Guys.
I’m making a backup DVD, using InstantCopy
The DVD has 2 audio options
PCM stereo, or dolby 5.1

One would usually assume that the dolby would be better than the stereo, but as far as file size goes, the PCM is 1.08GB as compared to the dolby 5.1 which is only 300mb.

which is better?

cheers

PCM is uncompressed. AC3 Dolby is compressed from the original by a twelfth. Using PCM will make the video stream compress more.