The only reason I have heard Plextor drives are good for ripping is because they are designed to be able to do block-accurate addressing on Audio CDs. This ensures a perfect rip without needing to do jitter correction in software. A complete discussion of this topic can be found here.

It is possible that, since the above-linked text was written, other drive makers have also added this feature to their drives. If that is the case, then the Plextor advantage is no longer as great as it used to be.