Overall, both drives perform quite similarly except in DAE, where the Pioneer was clearly superior. The Toshiba has speedier access times and disc copy results, but performs inconsistently when faced with a variety of discs. The Pioneer is a tad slower in access times and the disc copy, and its spiked transfer rate graphs raises some questions, but it is a much more consistent performer than the Toshiba in application-level tests.
In the end, recommending one over the other is difficult due to the different interfaces. Generally we compare within interfaces rather than between, but those without SCSI host adapters should not feel compelled to move to SCSI strictly for the purpose of getting the DVD-303S. However, those who already have a SCSI-based system would almost certainly be happier with the Pioneer. The consistent performance and DAE superiority are sufficient enough to rank it ahead of the Toshiba, when interface is no object.