#1, dual core xeon (better than single core xeon) and SAS (better than normal scsi)
SAS uses Serial transfer protocol to interface multiple devices hence lesser signaling overhead than parallel SCSI, resulting in higher speed.
No bus contention as SAS bus is point-to-point while SCSI bus is multidrop. Each device is connected by a dedicated bus to the initiator. Connection through expanders may appear to cause some contention, but this is transparent to the initiator.
SAS has no termination issues and does not require terminator packs like parallel SCSI.
SAS supports higher number of devices (> 16384) while Parallel SCSI limits it to 8, 16, or 32.
SAS supports higher transfer speed (1.5, 3.0 or 6.0 Gbps). The speed is realized on each initiator-target connection, hence higher throughput whereas in parallel SCSI the speed is shared across the entire multidrop bus.
SAS supports SATA devices.
SAS uses SCSI commands to interface with SAS End devices.