Depends on what you are going to use your computer for.
SCSI is very nice, if you many transfers going from multiple disks at the same time, it is then you start noticing the weakness of the ide bus. If you do video editing and such, then you would benefit alot from a faster disk. :-)
I i could afford it, i would have only scsi in my system, but sadly im poor so i gotta settle with ide disks. :cry: