Benq: Great writer, outstanding media suppoprt & media over speeding. But could been a faster reader.
NEC: Media support needs improvements, but writing quality is good. Fast but slightly picky reader. No official bitsetting for +R/RW
Pioneer: Media support need improvements, slow writer - but good writing quality, slow reader. No official bitsetting for +R/RW.
BenQ is the way to go in my opinion
When copying DVD-Discs I use this setup.
NEC ND-3520A: Reader since it reads +/-R media at 16x
BenQ DW1620A. Writer since it rocks. Using mostly 8x media and overspeeding it to 12x/16x writespeed with no problems. I use 99% +R media.
With this setup I could copy on the fly at 12x/16x with Nero.