The Pioneer is a good drive, but I believe it sells for around $130 at BestBuy minus a $30 mail in rebate (see link below). This makes the Pioneer a somewhat pricey drive.
The Plextor sells for $150 minus a $30 rebate, a $20 premium over the Pioneer.
Considering the expense of the Pioneer, I think you are better served paying $20 more and getting the Plextor. If you wanted to go cheaper, I’d tell you to buy the Benq 1620, which BestBuy doesn’t sell.
The initial reviews for the Plextor are not going to be glowing because there are still some bugs to be worked out in firmware, as Gamefreak stated. So if the review is what you are waiting on, well . . . expect to wait a little longer. The Plextor won’t reach it’s full potential for a little while.
But when it does, whoa buddy! It’s going to be something. I am setting myself up in opposition to all the hata’s. So maybe I’m a little biased, but I believe Plextor always comes through in the end.