s-ata is just serial ata, while ata is just . . . . ata
ATA has theoretical speeds of 100 and 133 mbps (hench ata/100 or ata/133)
Serial ATa has a theoretical speed of 150mbps, though it doesnt succeed 150 mbps. . .
the big difference why people go for s-ata is because the cable is smaller, and allows better airflow than ATA (IDE) cables
but its hard to install . . .