http://forums.computeractive.co.uk/thread.jsp?forum=7&thread=42516
Data transfer speed.
USB 2.0 is widely promoted as having a transfer speed of 480 Mbps -- a little faster than the original FireWire's 400 Mbps. However, this is a theoretical maximum for bulk transfers. Isochronous transfers, such as streamed audio and video, are limited to 192 Mbps (Section 5.9 of USB 2.0 spec.). In practice, the host controlled USB 2.0 bus is less efficient than FireWire and actual transfer speeds are rather lower. For a comparison see 'USB 2.0 Versus FireWire':
http://www.g4techtv.com/freshgear/features/39129/USB_20_Versus_FireWire.html
Quote: "Don't be confused by the rated speeds you see emblazoned across USB 2.0 and FireWire product boxes. Despite USB 2.0's 80 Kbps speed advantage over FireWire, our testing showed that the additional overhead of USB 2.0 made it slower than FireWire. For high-bandwidth devices such as external hard drives, the difference was as high as 70 percent."
Also see 'Flexible All-Rounder: External Drives from Western Digital with 200 and 250 GB':
http://www6.tomshardware.com/storage/20030411/wd_external_hd-09.html
Quote: "The performance of the Western Digital external combo drive in our tests displayed a trend that we have repeatedly observed with other hardware components: you can achieve a substantially better performance with FireWire than with USB 2.0, even though USB offers a theoretical throughput of 480 Mbps compared with "only" 400 Mbps with FireWire.
With FireWire, we achieved an excellent maximum data transfer rate of 38 MB/s. USB 2.0, on the other hand, maxed out at just 32 MB/s. So, the combo drive with FireWire is able to score 74 percent of the theoretically available maximum of 400 Mbps -- a fine achievement. USB 2.0 stops at 53 percent of its theoretical maximum."
Peer-to-peer operation.
FireWire is a bidirectional peer-to-peer bus where devices talk directly to each other. By contrast, USB is a host controlled bus that requires the computer's processor to act as a 'master of ceremonies'. This effectively halves the speed of inter-device transfers on the same bus since all the data has to travel to and fro via the host. The additional load on the processor can cause problems when transferring high-bandwidth asynchronous data such as video.
FireWire enables devices to be connected directly without the need for a computer -- a key requirement for consumer electronics as shown in 'Fire in the Wire -- The Future of Audio Interconnects':
http://www.audiorevolution.com/news/0702/11.firewire.shtml
BTW, most hard drives now have both connections and most expansion cards should support both as well. I'm not using firewire b/c my laptop came with the stupid 4-pin firewire port and I don't care about max performance. My externals are archives for all of the work/media/software I occasionally use.
