Should I use the direct SCSI version ?
If your drive is over 4GB and you cannot, or do not want to, use TD64 you MUST use the direct SCSI version otherwise it is not worth using the direct SCSI version with IDE disks. The SCSI emulation is slower than the read and write commands.
If you have a SCSI disk then try it out !
If you do not need it I suggest you avoid it.