The Raptor will outperform a 16mb cache 7200 rpm hard drive but not by much. If the 7200 rpm HDD has NCQ it will further close the gap, making the difference barely noticeable. Not to mention Raptors are loud, hot, and you will pay 2x as much for half the capacity. They are horribly overrated IMO.
Antec Super Lanboy
AMD 64 3800 S-939 Newcastle
MSI K8N Neo2 Platinum
1.5 GB pc 3200
WD 160 GB IDE
Viewsonic 22\" Widescreen 1680x1050
Coming Soon: Athlon 64 4000 San Diego/Z-5500/G7/Vista