Assuming you are using USB2, then the latency differences between FireWire and USB2 are more likely to be down to the external hardware and driver software used at each end rather than the differing connection technology, the speeds are fairly similar.

If you are on USB1 I would expect a siginifant improvement if you moved to USB2 or Firewire. I'd be liable to stick to USB2, there's more kit out there.

My understanding is that the only time Firewire has an absolute advantage over USB2 is when streaming synchronised Audio and Video; the Firewire data transmission specfication guarantees that synchronisation is maintained.