Kangaroo said:ATA to SATA is not the same as upgrading from AGP x4 to x8, it is definitely not the same percentage increase. But if you have a very simple choice, then choose SATA; it is ~12MB quicker.
It is not worth upgrading a motherboard for though
Kangaroo is correct. SATA does not reach 150 Mb/s. The only benefit is smaller wires and a 12(+/-) Mb increase.