Cotton canvas is the best all-round choice for a sack that is reused every year. Hessian looks better under a tree and survives less washing. Polyester is cheapest and is what most Australian retailers sell.
Polyester
The personalised sack most commonly sold in Australia is a 68cm by 48cm white polyester bag, resold under many different brand names with different design libraries printed on it. It is light, cheap and it slumps rather than stands. Prints are often vinyl, which peels after a couple of seasons.
Cotton canvas
At 280gsm, cotton canvas holds its shape when full, takes a cold machine wash, and holds a printed name rather than a stuck-on one. It folds flat for storage, which matters when it lives in a cupboard for eleven months.
Hessian
Jute has weight and texture, stands up on its own under a tree and photographs well. It is spot clean only, because jute shrinks and stiffens when soaked, and it does not fold as small.
How to choose
If the sack goes on a bed and gets handled hard, choose cotton. If it sits under a tree and appears in photographs, choose hessian.