As I have always said, it is not good to compare drives directly without mentioning what tests to base on.
BenQ DW1620 tries to write each media at the highest possible speeds whereas LG GSA-4163B and other LG DVD writers try to make it the safest possible speeds. DW1620 was mostly designed by Philips, the DVD+RW company whereas LG GSA-4163B was primarily designed by Hitachi, the DVD-RAM company.
It's also difficult to compare Plextor PX-716A and LG GSA-4163B. The AutoStrategy and other features in PX-716A don't mean much against LG GSA-4163B. Those who clearly prefer GSA-4163B to PX-716A are likely to dismiss some of those features while liking the P-CAV 16x speeds that also result in very low PIF numbers (and very good readback.) Those who sometimes use DVD-RAM media can't dismiss GSA-4163B. People who prefer PlexTools Professional for write quality tests will gladly pay additional money for PX-716A or PX-712A. For some people, LG DVD writers offer safer and longer warranty (often 1:1 instant replacement.) For some others, Plextor offers better support. Overall, there are more Plextor fans than LG fans on CDFreaks among those who post a lot and Plextor drives have far more often reviewed and discussed than LG drives on CDFreaks news, reviews, and community boards, but there are far more LG ODD users as LG is No. 1 in all of the ODD-related markets: CD-ROM drives, CD-R/-RW drives, DVD-ROM drives, CD/DVD combo drives, notebook/slim-type optical drives, and DVD writers. Plextor focuses on the niche market while LG targets at much larger and wider consumer groups. BenQ is yet too new. Year 2005 might prove well for BenQ and Philips partnership, but LG will continue to lead in all markets from CD-ROM drives and DVD players to Blu-ray and HD-DVD.