Well, the cool think about the Ethernet ones is that they’re their own node on your network, so they end up working kind of like a server. The data on the drive is accessible to any machine with access to the network. There’s no one host machine that has to be left on for others to get at the data.
I have a product from Netzero Netgear(?) that I plug a 500 gb USB drive into and then into my wireless router. All my computers in the house can access it.
When I first set it up I could access it from an IP address outside the network, but something isn’t working and I haven’t gotten around to getting it right to access it outside the network. Great idea, but kind of a stupid interface with the software.
Another drawback is the drive needs to be formatted in a proprietary formant for it to work. You can’t just plug a USB drive into it.