Yes, that's probably the first most important question to answer:
Do I want:
a) storage that will always require a host computer with a specific connector to work or;
b) a NAS that requires just a power cord and network connection and that can be taken anywhere and used with no special requirements?
Having lugged along various external drives to LAN nights and friends homes over the years, I'd go for a mini tower based NAS every time now.
But if you never envision it being connected to another computer or being able to access it from another device, (without having to turn on your main computer to interface it), then a big old box of dumb HDDs might be your thing.
