FOAM

Disadvantages:

Flimsy, unless it is hard foam which is difficult to come by, especially bought off the internet.
It is made in a factory and is petroleum based.
Unknown durability. May outgas chemicals.

Advantages:

Light.
Useful in therapeutic yoga applications.
Because it is soft, may be useful with frail and injured people or people with deformities or where gravity comes into play (when does it not?), as when held off the floor with a chance of dropping.

CORK

Disadvantages:

Can get hard and brittle with age and fall apart (like us).
Relies on glue to hold the small pieces together.
Gets dirty with skin oils unless sealed.

Advantages:

Firm yet resilient.
Will not mar furniture.
Supports natural cork production from the cork oak.
Can be made from sources like genuine recycled wine corks for instance.

BAMBOO

Disadvantages:

Can break and fall apart when dropped.
No proven durability.
It is a grass and needs to be made into lumber by factory processes.
Requires finishing.
Not sustainable when type converting or clearing of natural bamboo forests.
It is the food of the panda.

Advantages:

Light.
Cool, modern look.

WOOD

Disadvantages:

Heavy when solid.
Unless certified or from well managed forest, can come from primary forest sources.
Requires finishing.

Advantages:

Rugged.
Strong, trust inspiring.
Naturally beautiful.
Fixates carbon out of the atmosphere into a durable product.
Helps provide work in rural and domestic forest communities.