For performance, almost none. The drive itself is the same. SATA is the interface. It will be able to go faster in transfer than the old PATA (the old flat ribbon) when drive will be able to perform better.
Transfer speed for old ATA has stuck to ata133. SATA can go beyond that speed, but the current drive are not able to fully use the bandwidth of ATA133 and even ATA100.... But when future drive will start to increase throughtput then the faster interface will come into play.
So, the main reasons to go sata are smaller cable for easy cable manadgement, ready for future sata only (it will happen..but when???? optical drives are still at ata33...) or having a little edge in speed..as they can be faster in certain circumstance. But not enough to be called faster..
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