IDE = 133MB/s
SATA 1 = 143 MB/s (150)
SATA2 = 286 MB/s (300)
SATA3 = 500+ MB/s (600)

In other words IF you box is powerful enough then SATA, preferably AHCI mode, makes a big difference compared to IDE

Sata in AHCI mode (NCQ) is much better than IDE ever can go

http://en.wikipedia.org/wiki/Serial_ATA