I have Logitech Z-5500 speakers and I have a small problem. That is "true" surround sound in games. How do you have eveything configured? Do games support DD or DTS? What should be written on speakers LCD? I don't want Digital Dolby PLII because that is just matrix. I am interested in true surround sound but I am not sure how to get it.
Actually, you cannot compare them, since Dolby Digital is a method of data & audio compression technology, while DD PLII is a surround sound processing technology.
For music & movies, I'd say go with DTS, since it tends to have more low end for a richer bass. But it's upto your personal preferences. Listen to both DTS & DD & then make your choice.