15KRPM SCSI is obviously faster than a 10KRPM Raptor... beats it in seek time, STR, and everything else.
The Raptor is also tuned more for desktop/light server usage, NOT heavy multi-user database loads. This hurts it even more in multi-user benchmarks (but makes it competitive for single-user machines). But even if it was, it physically couldn't keep up with a 15KRPM drive.