I recently bought a fastata MKIII (elbox), but it is defected. So i cannot compare it really. A few days after I sell some servers for one of my customers, then he brought me some old (68 pin) scsi drive for free, these hdd used in the old servers. He heard about my crazy hobby (amiga) and years ago he saw some amiga, and it used scsi, so he think it is good for me. And only then i realized i have a built in scsi port in my amiga. (blizzard ppc) So i after some speed up again in my system. Anyway scsi and sata/ide technology iis mostly the same nowadays in pc, only servers has some benefits, but in amiga the benefits are many:
Not using cpu power.
If i use more than one unit the scsi bus won't be slowing down then an ide.
Using more than 4 unit.