Either round or square port is appropriate, really. Round intake ports are in the cast iron lined hi-torque, closed transfer type cylinders. By design, the enclosed transfers restrict the volume of fuel mix while controlling the flow for better efficiency.
Square intake ports are for the aluminum open transfer cylinders with the chome cylinder wall lining. Newbs and the uninformed often assume these are crappier than the hi-torque types but, in reality, the open transfers are far less restricted resulting in more free reving high RPM.
Strangely enough, I've found the open transfer cylinders to be more robust and more forgiving to neglect and abuse than the cast iron sleeved closed transfer cylinders.