If the network has Gigabit port and the computer has Gigabit network plug then on paper the network way is quicker than firewire 800..
has to be 10/100/1000 ethernet port to 10/100/1000 ethernet port to get the full speed..
If computer has 10/100 ethernet port and you use an ethernet network drive then firewire connected harddrive even 1394a (firewire 400) would be quicker

hope you could understand my explantion