2) My understanding is that this varies widely for a number of reasons, including the very program used to assess the quality of the media. My understanding is that these software report what the drive is saying, and does not, itself, judge the media.
I have been trying to get a better hold of the issues, myself. My gut feeling is that Taiyo Yuden is always among the very best, but this does not always bear out, as far as I can tell. As an example, the Ricoh G04 seems to work very well with the Pioneer 106, and is almost universally recommended as the media for that drive. I think that one of the online stores even says that it is the best for that drive.
What drive do you use?