The instructions in VV4 suggest using the GOOD setting for rendering the final output, since using BEST would give you very long rendering times. I've been using BEST anyway. What is the actual final quality difference between the two? Is it noticeable?
I think that the primary difference between good and best is the scaling algorithm that's used when zooming in. It's been discussed before, so a search in either this forum or the manual should give you the information you need.
I always set my default at Best, even though renders are longer. It's an absolute necessity if there is any pan/crop, track motion, or working with interlaced video. Try rendering any of this in Good and see the difference.
There is a lengthy thread about this that was active a few days ago. It relates to the type of interpolation that is used for some effects. Most of the time, good is as good as best (If that makes sense!)