SCSI has no cpu load as far as i know. It has its own microprocessor that does the work instead of the cpu.
SCSI is "faster" because the devices using the technology usually have a higher spindle rate than IDE devices.
Higher spindle rate = lower latency.
Unless you're doing many things at the same time, like listening to mp3s and playing some cpu mongering game, go with IDE.
Unless you really want to spend the money....
In my opinion, if there are 24x IDE writers available, there's really no point in spending extra cas on SCSI. How long will it take to make a cd??? 2 minutes?