www.StorageReview.com has benchmarks for desktop and server use.
SCSI is optimized for servers making a lot of seeks, and for durability. Capacity is lower, price is much higher, and performance can actually be lower in desktop applications.
Overall performance depends on platter density, cache buffer, spindle speed, and design quality.
Noise and heat are also factors to consider, 7200 RPM SATA drives from Samsung and Seagate can run much cooler and quieter than a raptor or SCSI drive while offering almost the same performance on desktop apps.