A multiple physical drive system can be more efficient than a one large drive system - assuming the drives are allocated properly and located on separate channels (except for SCSI where several drives can share one channel with ease). I have three physical drives with all the scratch space, TEMP folders, printer spooler, swap file, etc. (IOW most of the writes) on a partition on one of them away from the OS and have had no drive (or even file) corruption in over a year. Knock on wood!
.bh.