It depends on what you're doing with Firewire as opposed to USB 1.1.

If you are just transferring a digital file, then what Marc said applies. Same file at the end, but USB 1.1 takes way longer than Firewire.

However, if you are capturing an analogue video source via USB 1.1 versus Firewire, then yes, you will see a difference in the resulting file.

But that difference is because Firewire is a much faster protocol that USB 1.1 is. So, when capturing with USB 1.1, the resolution has to be turned down, and some frames may be lost because they couldn't be transferred fast enough.

...jim