Firewire is a lot more flexible because it's just a serial digital standard for high bandwidth applications. It' doesn't much care what information is being carried and it has a respectable amount of bandwidth. DVI on the other hand is a parallel standard, I believe, and only carries video. I'm not aware of anyone using Firewire to transfer video to a monitor at this point but I don't see why they couldn't. It is the digital transmission standard of choice for DVD-Audio, and, as you mentioned, offers some unique network capabilities as well.