Tom, If I remember correctly, the one marked with the ds has Daz specific materials. The one with the dpc has all the normal files. The file size is usually (always?) larger on the dpc one.
What I'm trying to say is that those that don't use Daz|Studio don't need the second file, while those that do us it do need it. D|S will read everything from poser except lights and procedural materials... I think that's right anyway.

Hope that helps some.