The difference in the access times between the MD2 USB and Firewire can only be explained by much longer latencies within the USB protocol. I tried the benchmark several times to make sure that those results are reliable. Western Digital's FireWire drive is faster due to the faster hard drive.
In my opinion, the CPU utilization test is no longer useful with today's processors. In addition, these storage devices don't claim to be high-end drives that minimize CPU usage. However, it is interesting to see that the CPU utilization with the FireWire drive is higher than with the USB drive on our test system (TI Firewire controller).