It's all a matter of the manufacturing code of the DVD media. You'll need a program like DVD Identifier to read the media code, and there's no way to determine the code by looking at the packaging.
Some of the best media comes from Japan and includes Ritek (the past few TDK and Sony DVD+R discs I've gotten have been Ritek). Generally, the higher burning speed indicates higher quality media (4x, 6x, 8x), and the 2x or lower media is usually lower grade.
You'll just have to try a particular brand and see. I've had good results with the KHypermedia DVD+R media from Officemax, even though it only burns at 2.4x. It all depends on your particular burner.