This has been a topic of various threads, but this looks like a useful source of information
http://www.digitalfaq.com/media/dvdmedia.htmDVD media quality check[/link]
Some time ago I struck problems with Ritek (which was popular at the time) and Imation I learned to avoid, so these days stick with Verbatim. These tables confirm that those problems were related to inherent media quality.