[Threlly]

Firewire interfaces have their own chipset that handles data transfer, and they have a bit of oomph too.
Firewire can sustain 400mbps transfer rate.
All data has bit locked synchronisation.
It was designed for Video & Audio.

USB uses your CPU.
USB sends data in lumps.
USB can PEAK at 480mbps in exceptional circumstances.
Synchronisation can not be guaranteed, only attempted.
It was never designed for Audio, Video or Midi.
It was designed for printers, scanners, keyboards and low level bulk data transfer (Digital cameras, MP3 players)

Look up USB & Firewire on Wikipedia.

Hope to god your machine has Firewire and wonder why the hell Access put USB1.1 on their mega-synth ?