1) You read speed on DVD Writable Discs is exactly where it should be - 10x.
2) I've had similar exteriences with the MCC004 MIT's, but not always. Most of the time they burn at 16x. However, I usually use Nero at 12x. I find the 12x burns much better and only about 30 seconds slower.
3) I saw the specs on your system in the BenQ forum and it's about 3 times faster than the two systems that I run LG's on. You don't need much of a system to keep up with a burner as long as your not doing other things at the same time.
4) Just a While Guess about DVD decrypter: It reports in a similar manner with some (but not all) media - so maybe there are multiple recording strategies in the firmware for certain MID's. Maybe the burning software is allowed to choose the optimal strategy????
The more I think about it, there probably are multiple entries left in on purpose as "Rom storage place holders" and the burner just uses the first one that matches the MID of the Disc - also guessing here!