Print server vs. printer sharing on Windows Server
It is pretty much what you assume it to be, additional features. As you have experienced, you'll still be able to share printers and act as a "print server" without the role. However, the role provides things like the Printer Management console for ease of management, quick deployment through Group Policy (if you were using a AD Domain). You can also install things like the LDP service for printing from Unix based hosts, and Internet Printing.