I have to agree with TimC, a Transfer Rate Test usually identifies a good or bad burn.
The Disc Quality Test basically tells you more about the quality and longevity of the disc. But it doesn't necessarily tell you how well the disc will play in your DVD Player.
The Disc Quality Test should always be secondary to a TRT in my opinion. If you've got a good TRT then your Quality Score will most likely be higher than 80-85% which is good enough for good playback in most DVD Players.