I think scsi is a superior to ide in everyway, except cost. A good scsi card will cost at least as much a dvd drive. If you have scsi already, definatly go for the scsi drive. check that the ribbon connectors are compatible with your card.
Scsi isn't cost effective for most people. and if your not familiar with it, well,there's a learning curve. If you want to run a server or A/V editing, use portable external drives, or chains of peripherals and hard drives then scsi's for you.