Ironic since your ava is of an aero-ported box.A vent is a port, and vice versa. Your question is pertaining to vent shape, being round or square?
It is all preference. I do not like using round because generally all the air around the port would be dead and you must accomodate the size of your enclosure to make up for that space. It is convenient to reuse them and change tuning, however.