Square pots or round?

Can you recycle black pots where you are, Veggie? If you can, then ditch the black ones and keep the orange ones, if you can't recycle black, then keep the black and ditch the orange, then keep the square and ditch the round.

I like square because they fit in trays better, and roots don't end up circling the pot so much.

There must be advantages to round ones or they wouldn't be used so much commercially. Perhaps it is as you say, they take less filling.