go with the 55g drum they are cheaper, and i would dig out a circle for the pot a few inchs in the ground, roots grow out from smartpots and should go into the ground
the roots won't grow far. the fabric is designed to 'choke' the root
at the bag interface & cause a nodule to form.
I don't think the roots will grow out into the adjoining soil.
They are root pruning cloth bags.