Hi Dustin,
I’m in the unique position of owning two RAID5 systems: one of them is a Pegasus thunderbolt RAID, while the other is a Sans Digital USB3/eSATA enclosure. Both setups have 4 7200rpm disks inside.
Benchmark wise, there’s no question, the Pegasus unit wins. But do I “feel” that difference while I’m editing? Hardly, if ever.
The Pegasus will do about 450MB/sec read, 300MB/sec write. The Sans Digital will do 170MB/sec read and 100MB/sec write with USB3. When I connect it with eSATA (via my lacie thunderbolt/eSATA adapter) it will do about 230MB/sec read, 140MB/sec write.
Of course, both the Promise and Sans Digital systems slow down substantially as they fill up, so remember that those numbers are with at least 60% free space. Hope this helps.
It should also be noted that I could buy 3 Sans Digital enclosures (including hard drives) for the price of 1 Pegasus RAID. At least those were the prices when I purchased them.