I agree with a lot of you comments Bark, but I was talking about FW800 versus internal standard sata drives. Here are the facts on my Mac Mini using BlackMagic Disk Speed Test.
MM Internal Scorpio Blue 1TB - Write 95MB/s Read 94MB/s (secondary non-boot drive on my MMi7Quad)
MM Internal Scorpio Black 500GB - Write 78MB/s Read 78MB/s (secondary non-boot drive on my MMi5)
External Scorpio Blue 1TB (in a WD FW800 enclosure) Write 64MB/s Read 68MB/s
External OWC Mercury Elite Dual Pro (Seagate Barracuda XT 7400rpm 4TB times two on FW800) Write 71MB/s Read 55MB/s
External VoyagerQ Dock with Toshi 5400rpm laptop drive - Write 45MB/s Read 33MB/s
That is my experience with many drives with two MacMinis. Internal data speeds on both Blue and Black Scorpio drives beat all external FW800 drives including my 3.5" Barracuda XTs that have 7200rpm spin speed with 128MB Cache. Note the two identical Scorpio Blue drives with a 30% drop in transfer speed with the FW800.
Each to their own. We all have our preferences, but that is my practical experience.
Silver.
And I'm sure those numbers are for large sustained file transfer, not for random blocks which is more of an indication of App loading performance, swap file efficiency etc...
Had you used either the same drive in each enclosure and run tests on that one drive to compare the speed differences of each interface, those number might mean something but all they show is that different brands of drive have different performance regardless of the interface used.
For example, my drives are on a PCI SATA 1.5Gb/s controller so they're using the same interface, my Mac's PCI slots are far too slow to even come close to full speed SATA 1.5Gb/s but my SSD gets higher MB/s than my Caviar Black drive because it's an SSD.
Once I do 4K random tests, the hard drive is 2Mb/s, the SSD is 20Mb/s+, for sustained read/write of large files, they're within 10-15Mb of each other, simply because the bandwidth of the PCI SATA card seems to be limited to just under 90Mb/s. If I ran the SSD on a full bandwidth SATA 3Gb/s connection in a Mac Pro or 2009 and above Mac Mini, it would run at over 250Mb/s but the hard drive would still be it's current speeds because it doesn't saturate the bandwidth of the interface.
I ran some benchmark with Xbench when I got the SSD last year for comparison. They speak for themselves.
[EDIT] several sources online, this...
https://forums.macrumors.com/threads/1186048/
...particularly show that Firewire 800 is limited to 70Mb/s so I see your point with those numbers but at the same time, sustained throughput is irrelevant.