Just read from someone who works for a major DVD-Recordable manufacturer, and he commented that there was a great variation among Sony DVD burners in terms of media burning compatibility, and this seems to be confirmed by numerous owners’ complaint of not burning DVD-R discs at 4X. I thought Sony fixed this problem by introducing the DRU-510A with a different hardware, but apparently not. So you are basically at the mercy of pure luck.
Also the latest introduction of the DRU-530A turns out to be an OEM of the Optorite DD0401, except it has a less functional firmware with no HD-BURN support and no 8X writing for certain 4X +R discs. Who wants to pay $100 more for a Sony labeled Optorite OEM with less function?
I am sure you’ll be very happy with your Plextor model.