I'll attest to the Benq 1650 having better scans at 8x and 12x speed,using quality media. Same results with my 1640. With my benq drives and my quality media,slow burning produces way too many crc errors.
Example: MCC-004. I use my normal process of ripping with dvd shrink and autoburn with nero 126.96.36.199b. When i'd go to sleep,leave for work,or busy-I'd set it up to burn at 2.4x and auto shutdown. Well,a few weeks later,I went to re-rip some backups. Bam-Crc errors.They still played ok,just wouldn't re-rip. I narrowed it down to those 2.4x burns. I re-backed the originals again,using 4x. Verbatim 16x media were designed to be burned faster,not slower. On another brand,results may be the opposite.
Beware of 2.4x burning with MCC-004 media if using a benq 1640/1650. Anyone burning that slow with a benq,try re-ripping one of those backups and see if you can get it back onto your harddrive without a crc error.That's a pretty easy test to see how actually good they are. Scans are ok,but a backup disc that I can't re-rip-Is of no use to me.
My latest version of Nero 188.8.131.52 came with my 1650 a couple months ago,via canada.My old version didn't have nero's disc quality scan program-grayed out. This newer oem disc does. For MCC-004 media,my benqs scan best at 8x. My 12x tests scanned a hair less,but way better than the 4x tests.
Got a Q 1640 or 1650 and using quality MCC/Hitachi/Ritek-R03/or Taiyo yuden?definitely 8x!
Then there's still the typical picky player.They can do some weird things. I burn according to how may scans give me the fewest errors and my stand alone players and pc drives playability.