what is the advantage fiber vs 1000 Mbps

What is the advantage or what would be the advantage between fiber optic and 1000 mbps Ethernet cards. we are attempting to setup new blade servers for a non-profit agency and needed to know if the cost between the two would be an advantage to us or not. we are looking at hp blade server encloseure with f-gbe2 and bl2op blade bundle. any suggestions.