got a few types, one is connect direct to comp (direct attached storage, DAS) or connect to network (network attached storage, NAS), both got their own difference... many new DAS use USB 3.0, which is much faster than gigabit ethernet, but it is usually bottlenecked by the spinning harddisk (which limits transfer rate to about 80MB/s)...
you talk about bufflo, which type? nas or das? afaik, they make both types...