PNG offers the highest image quality. But comes at the cost of increased RAM requirements. It probably takes much longer to pre-load all the textures and may cause stuttering if not pre-loaded.
DDS on the other hand offers lower image quality, but not that much. In the future I intend to update the DDS pack with the new BC7 technique so that the DDS textures are almost up to par with the PNG textures. DDS loads much faster does not cause as much stuttering as PNG (with pre-loading DDS textures there is virtually no stuttering at all). DDS also requires significantly less RAM.
Regarding content, but the PNG and DDS pack offers the same content and both are up to date. So it is up to you to pick your preference. Both have their pros and cons.
DDS on the other hand offers lower image quality, but not that much. In the future I intend to update the DDS pack with the new BC7 technique so that the DDS textures are almost up to par with the PNG textures. DDS loads much faster does not cause as much stuttering as PNG (with pre-loading DDS textures there is virtually no stuttering at all). DDS also requires significantly less RAM.
Regarding content, but the PNG and DDS pack offers the same content and both are up to date. So it is up to you to pick your preference. Both have their pros and cons.