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Although FW400 can be faster than USB2.0 I've seen more variability on chipsets. ..."
FireWire 400 is slightly faster than USB 2.0, generally, especially in bulk file transfers like video files. With small file transfers like syncing cell phones, etc. the performance differences are difficult to detect. FW800 is twice as fast as either.
There are some performance differences in the chip set used in FireWire and USB 2.0:
FW connectivity to multiple cameras is best through the Agere' chip set. Up to 8 DV cameras can be connected with this FW chip set, and all 8 can feed video "simultaneously" without frame drops. Lucent owns the manufacturing rights to the Agere' chip set, but this applies to very recent Lucent chips.
FW800 and FW400 hubs with the recent Texas Instruments chips are best = better data flow through the multiports of the hub. These are ubiquitous in modern hubs and FireWire over fiber extensions.
NEC used to make hub and port card chip sets that were considered the slowest, but quite reliable. NEC no longer makes FW chips.
USB 1.1 and 2.0 connectivity to Cypress chip set in keyboards, mice, joysticks and printers are the best, most reliable and most cross compatible, WinPC, Apple Mac, Linux, Unix, etc. (There is now only one system that requires "special" USB chips for the host port card and motherboard connections, Sun Solarus, all other Sun systems = no problems.)
For USB audio (DAC) there is huge controversies as to which is best ... TI and several British and Danish chip houses seem to be in the fore.
Because of the peer to peer topology, better "handshaking", significantly lower "jitter" specs, and better bandwidth, FireWire audio (DAC / ACD) are vastly superior to USB audio (DAC) chip sets. FireWire 400 can stream eight (8), bi-directional channels of 24 bit / 96k audio ... USB 2.0 but two 24 bit channels, one way at a time, only.
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Mercenary announcement: I work for USBStuff.com and FireWireStuff.com, since 1996. The above information is mostly from hands on experience and tech support Q&A.
