The BenQ is a good drive, albeit a bit limited with the DL, DVD-R and DVD+RW speed. It does have the ability to scan for errors which is nice. I refuse to believe that it doesn't have riplock, it's kind of a legal requirement.....
If you're willing to use the hacked firmware for the 3520, then the NEC wipes the floor with it in terms of write speed and media compatibility - like writing most 4x media at 8x and 8x media at 12-16x, no riplock, region-free, bitsetting on DVD+R and DL. Unfortunately, with the stock firmware, the NEC's are a bit crap....
Basically if you prefer quality to speed, and prefer DVD+R to DVD-R, then get the BenQ, otherwise get the NEC.