In an nutshell, use “Best” if you have a lot of titles and/or stills. Otherwise, “Good” is good enough.
Sony’s knowledgebase article says:
“Best” uses bicubic scaling with integration, while “Good” uses bilinear without integration. You will have a hard time telling the difference, but use “Best” if you are using high resolution stills or video that are getting scaled down to the final output size. “Good” may have bad artifacts on the near-horizontal edges, while “Best” will look great.”
Dr. Dropout gives more detail in the draft preview good best thread.