Memorex is bad all around. Even their lightscribe won't hold an image.
From what I've read lately on the various innernets, for SL Taiyo Yuden is the way to go, but they aren't as reliable for DL. Verbatim is king of DL. This is all subject to change on a moment-by-moment basis, of course. As for myself, I've never burned a TY or VB coaster. Memorex, however, is another story.