Hardware

Mainly, it's politics.


Yes, Firewire is superior to USB1/2 in every metric; throughput, latency, bus power, number of devices, etc. Plus Firewire is more reliable and compatible than USB, since Firewire devices do not require any drivers to be installed in your OS - USB on the other hand requires drivers for every single USB device.


USB and firewire both came about in the mid 1990's. USB was developed by a consortium led by intel. Firewire was developed by Apple.

For the first iteration of each, they did not compete. USB was only 1.5 Mbits, and Firewire was 400 Mbits. No comparison. USB was purely for keyboards, mice, joysticks, and other low speed devices.


The next iteration of USB, version 2.0, brought a large speed increase, from 1.5 Mbits to 480 Mbits. At first glance, one might think that USB2's 480 Mbits is faster than Firewire's 400 Mbits. Not in the real world however, where Firewire would deliver a sustained 38 MB/s while USB2 could barely manage 30 MB/s.


But back to the reason that USB became ubiquitous, while Firewire was more of a niche product: Politics.


Intel, having played a lead role in the development of USB, had a vested interest in USB's success. So they integrated a USB host controller into every single motherboard chipset. This gave every motherboard out there USB ports as standard, built-in with the motherboard. Firewire on the other hand, required the consumer to add a PCI card to their machine to gain Firewire ports. This immediately gives USB a market penetration advantage.


The second prong of intel's attack was on laptops. Intel added Firewire to laptop chip sets, but did so in a very crippled manner. Instead of using a standard firewire host port, they used a power-less device port. So the mini firewire port you find on many laptops does not provide ANY bus power at all - you're required to use a separete power adapter. Imagine if laptop makers put micro-USB device ports on laptops, and removed the bus power, requiring to plug in a separate A/C adapter to use even a thumb drive! It would be absurd, right? Well that's what they did to cripple Firewire.


So while Firewire is technically superior to USB in every way, intel's politics drove it into a niche role, while the inferior USB became ubiquitous.

Firewire 400 beat USB2 by a large performance margin. Firewire 800 was faster still, delivering triple the real-world performance of USB2. The newly released USB3 however ups the ante. Originally there was talk of Firewire 1600 or Firewire 3200, but that has apparently been scrapped in favor of Thunderbolt.

Personally, the only things I use USB for is keyboard, mouse, and joystick. Everything else is on Firewire 800: DVD burner, hard drives, flat bed scanner, HD Audio mixer, and HD video camera.

Another thing to keep in mind -- every time they make an interface faster or better, it either needs more expensive cables, or shorter cables. This is because, the faster the signal, the more it reduces with distance. Look what increasing the speed of Ethernet did to its maximum lengths:

Code:

Interface   Speed       Max-length
  10base5    10  Mbit   500 meters on coax
  10baseT    10  Mbit   185 meters on two pairs
 100baseT    100 Mbit   100 meters on two pairs
1000baseT   1000 MBit  	100 meters on FOUR pairs with error-correction

They're trying to make Thunderbolt via viber optic popular, which can avoid this to a degree.