Papier Mache
When in form of newspaper it's fragile and easy to rip or crumble, but if folded multiple times it becomes hard to bend further. That's why it was hard for me to make it of a proper shape in one of my sculptures. After I did make shapes I had to cover them with a masking tape so they won't unfold - as the paper would do otherwise.
Papier mache is a paper (in our case a newspaper) covered in a water-glue substance. Because of water it matches the shape of whatever it's been placed on and because of glue (that is in greater amount than the water) it's very sticky. After drying, if the substance has proper glue to water ratio, the paper stucks to the surface and becomes very hard and sturdy and hard. I haven't placed several layers of it but if I would then the sculpture would retain the shape more properly, that is it wouldn't bend any more in any place.
Wirework
Depending on a metal and the thickness, wire is either hard or easy to bend. The normal wire we used (dark one, don't know the metal) was hard enough to retain its shape and be used for the skeletal base, but it was neither hard or easy to bend (except when I had to wrap it tightly or unfold). Copper and silver wires were much softer, but not able to be used as support. I used them for details instead, since I could bend them very easily.
I also used wire for both other sculptures: in the papier mache I used a wire (protected in some green coverage) to join all the parts together and the face details, whereas in clay I used it for wings.
(Airdry DAS) Clay
While wet, the clay is very mouldy: it can be shaped quite easily, I think that depends on the type. The airdry clay we used was quite tricky especially when I tried to merge pieces together into one. I also had to constantly cover it in water so it will stay elastic and bendy. Since the clay is heavy I had to think of a pose for the sculpture that would require the least support. For others I would use wire or something to support it after it dries. When dry it does keep the shape but can be easily destroyed from fall. When dry it also retains its shape forever.
There are some clay types, such as plasticine, that do not dry and are used for animations but I didn't use the plasticine for the sculpture task, though I wanted to.