For a single drive, IDE is theoretically about as fast as SATA... Except that the drive manufacturers quit putting new tech into the IDE drives a few years ago. It isn't necessarily the interface that makes SATA drives faster now, but the drives themselves are better too. The good drive tech just isn't used on the IDE drives anymore.
I got "identical" IDE and SATA drives a few years ago, and although neither drive came close to fully saturating either the IDE or SATA bandwidth, the SATA drive was about 20% faster than the IDE drive for both seeks and transfer rate. The IDE drive wasn't crippled since it was just as fast as an identical one I'd purchased a few years earlier, but the SATA one had a new controller chip, better cache, better internals overall.
So, go SATA even if not buying a huge new drive. Also the price should be about the same, maybe even lower per GB for SATA.