Congratulations on your new burner. That scan looks excellent!
I don’t really understand why there is such a huge difference in the NEC 355x/455x series scanning abilities from drive to drive, but unfortunately the scanning behaviour is unpredictable - even with the same drive and the same media.
My NEC 4551 is a horrible DVD scanner, but it isn’t even consistently horrible, so now I only use it for scanning occasionally to get a good laugh. It scans CDs reliably though, but I cannot guarantee that other 355x/455x drives also scan CDs reliably.
So I would keep scanning DVDs with the BenQ 1640 if I were you!