Well.. that all depends. It has a higher max transfer rate 150 vs IDE's 133. And, thanks to those smart kids at MIT, you can take advantage of RAID. RAID can be used to mirror everything on two drives.. in case 1 drive craps out; it can be used to treat up to (4 I think) drives as one single drive. And it can do a few other things.. can't remember them all.
Is it that much better than IDE? Well, if you don't really have any interest in utilizing RAID then there's no reason to upgrade since, most likely, you're not going to notice the increase in transfer rates.
But, its all up to you
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