I've left at the factory default, "Good" . .. apparently we can't register the difference. There has been a discussion about this and you may wish to read those threads to add some more knowledge to your VIdTank !
Hi Grazie. Assuming that Best is better than Good in certain circumstances (must be, right, otherwise there would be no such setting?), the problem is that the 20 second sample might not be representative of the condition where Best makes a difference. With a different sample, maybe Best would be noticeably better and worth the extra rendering time?
Anyway, since I live in Singapore, I tend to be more "kiasu" (meaning afraid to lose out), so I always select Best for rendering quality. And to return to the original question, after setting the rendering quality to Best, I saved the setting as a new preset (such as "DV PAL Best") which is easy to find the next time I need it.