PVC foamboard for terrain boards?

[Smokeyrone]

I'm interested in what the difference is between 'blue board' and so many of the other foam insulation boards still available cheaply?

Blue or pink board is far superior to all other foams.  Stronger, denser, and sands/carves better.   

[FifteensAway]

Here in US, foam building insulation board (in a palish yellow sort of color), is a good choice.  Or you can travel my road and use wood and power tools.  Very durable but a bit heavy - wouldn't work well for those who have to travel on hire transportation/public transit, etc.  I do use a small amount of foam on some pieces.

[dwbullock]

My local home improvement stores have begun carrying a greenish foam insulation board.

It is somewhat similar to floral foam, though less 'gritty.'  I must say, though, that it sucks compared to the old pink or blue stuff.  Tends to be a bit more brittle, and doesn't sand as smooth.