Xonar DS or Xonar DX?

And one more question, what do you guys think sounds better? DTS or Dolby digital? I prefer DTS.

1: Movies that area ALREADY encoded in DTS will be able to transfer their audio through optical without issue on either card. 5.1 audio that is not already encoded in Dolby/DTS formats (games mostly) will be encoded to whichever format the card supports (Dolby for the DX, DTS for the DS).

2: Both are lossy formats, and inferior to uncompressed audio. DTS has a slightly higher bitrate though, though I doubt thats perceptible.