If you want to post scans in the LiteOn DVD forum you should use 8x scans because that is the chosen standard scanning speed.
As for which is the "correct" or "best" scanning speed, the answer is that they are both right and they are both wrong. They each present a point of view about the quality of a disc, but one isn't more correct than the other.
There is ongoing debate as to which drives are more reliable, which scanning speed is more reliable, whether quality scans are more or less reliable than transfer tests, and so on. What it all boils down to is that no single test will be able to tell you all you need to know about the "quality" of a disc every time you use that test.
Personally I find that 16x scans on my LiteOn 165P6S are more useful than slower speed scans most of the time, but they are hard to compare to what other people post on these forums.