If the printer is shared it makes more sense to use Ethernet to connect the printer directly into the network, that way you won't have to use a "host" computer that has to be turned on whenever somebody wants to print something.
If you're the only person who uses the printer, however, then it makes more sense to wire the printer directly into your computer via USB. Assuming you're not on a laptop of course, in which case connecting the printer to a wireless access point via Ethernet would make more sense so you can print wirelessly.