I've been sent this link (in Spanish) by a friend of mine. On this page you'll find a list of the different DVD brands and their quality divided into 4 types 1 being the most dependable and 4 being the least. There is also information regarding the tell-tale signs that separate good from bad quality discs. This is the link: http://tecmarket.uni.cc/DVDinfo/dvdguidebody.html At the bottom of the page you'll find a series of related links (mostly in English). I tried to find an English language equivalent, but couldn't (sorry). If you can't read Spanish you might be able to understand the page by entering it through the translate page option at Google. Any comments on this information will be welcome.
Go here http://babelfish.altavista.com/ And place this link http://tecmarket.uni.cc/DVDinfo/dvdguidebody.html in the translate a web page section, then select Spanish to English. If it doesent work, try it again, it will.