Previously I did some tests on various internal and external drives.  I just received a brand new Western Digital Passsport Studio drive.  This 500 Gb, 2.5 in, portable drive has three interfaces so I felt it would be a great way to test a comparision between USB2, Firewire 400 and Firewire 800.  I used Drive Genius to do the benchmarking.  It tests four different parameters, but to keep it simple the following charts are only for Random Write.  The green bar is the tested drive and the blue is the standard for a MacBook Pro internal drive.

My tests confirm that the slowest is USB2, followed by Firewire 400.  The Firewire 800 drive was MUCH faster.  Look at the charts to get a feel of how big of a difference the interface makes.  I also include a chart from the prior log entry of the internal 7200 rpm drive.

USB2

USB2 Interface

Firewire 400

Firewire 400

Firewire 800

Firewire 800

Internal 7200 rpm drive