Ritek G05 - Approximately 1/3 of a spindle of 50 have a physical defect consisting of shallow smooth conical depressions about 1/4 inch wide that cause the dye layer to be way out of range of the laser. Burns fail in the worst case, 1/8th inch pale dark spots appear on the disks that burn okay (when the depressions are shallow enough so that the laser can compensate).
Ritek G05 - The dye layers of all Ritek DVD media are visibly uneven (appear splotchy). This includes most Maxell DVD media sold in the U.S., which are rebranded Ritek.
Some Taiyo Yuden disks (of the "shiny silver thermal laquer" type) have a tendency to delaminate at the inner edge of the hub more easily than other brands of disc, and more easily than the "inkjet printable" styles of Taiyo Yuden discs. It appears to me that the adhesive used to laminate the discs is incompletely cured in the hub area of these discs.
In spite of that, Taiyo Yuden are possibly the finest media available. You may however see some that have a faint haze over the surface. This seems to make no difference to players, but may cause them to burn at only the stated rate (for example at 8X for 8X media) instead of the usual 1-1/2 times the stated rate (12X for 8X media) which is often possible with Taiyo Yuden discs. (Some burner firmware versions may prevent burning at higher than the rated speed.)
Maxell 16x DVD+R exhibit radial linear defects up to 1 inch long. After burning a light, sharply defined line can be seen. These discs often fail to be read on drives other than the one used to burn them. Whereas they are unreliable for data applications, they may nevertheless work fine in commercial dvd players.
Verbatim Dual-Layer discs are the only one that burn reliably using growisofs under Linux. They will burn 100% reliably with speed=2 set. 90% reliably at speed=4. Use this command:
Many Pioneer burners create DVD's that are unreadable in other brands of burner. If you have a large number of DVD's that you burned with a Pioneer drive, keep the Pioneer drive around just in case you wind up needing to copy a DVD you burned with it. This will save you a lot of grief. I recommend sticking with Plextor burners until I change my mind again ;^)