I would rather say that high-speed scanning shows you a different point of view than low speed scanning. Scanning at multiple speeds on a drive will tell you more than just scanning at a single speed. Scanning at multiple speeds in multiple drives will tell you even more. Combining this with Read Transfer Tests in some picky drives will tell you even more.
I have recently tested a couple of mediocre/bad discs in all my scanning drives except my Optiarc 7173 and Plextor 760 and at multiple speeds. The results have been an eye opener and I'm leaning more towards high-speed scanning than I ever did before.
I need to perform tests in my Optiarc 7173 and Plextor 760 and then I will present the results in some way on the forum.
I can already tell you that a specific problem is shown in multiple drives, but only at 16x scanning speed in my LiteOn drives, with not the slightest sign of the problem at 12x and slower scanning speeds. Some drives show the problem in TRT tests and some don't.
I scan @ 4x with jitter in cdspeed to find out the jitter. Then I go again at a high speed. 8x or higher just to see how badly the jitter effects scanning.
Based on my experience, if you want to scan at two speeds I suggest 4x with jitter and 16x (without jitter).
For scans posted in the LiteOn forum you need to use 8x scanning speed on the 5S drives and later, however.