[Nacho libre]

Would go with sheet styrene plastic as it's is pretty solid and simple to cut and shape.

 

[Nacho libre]

Agreed plasticard all the way. It's more solid, won't warp with paint or washes, can have battle damage cut into it more easily without going fibrous and can be stripped like any other plastic model if you mess up the paint scheme.
The only thing I tend to use card for is adding detailing to flat walls on buildings. Usually the building will be something more durable than card.

Agreed and I love the new profile pic.