We use the mesh Doon speaks of, so far it is by far the best material we have seen.
Plywood = too heavy and rain will soon delaminate it plus its expensive.
Snowfence = holes too big and it tears easily (fairly brittle) especially after its been out in the weather for awhile.
Plastic Mesh / screen = expensive and it also tears easily.
Netting = poor cover, pita to wook with.
Coroplast = similar cost as plywood but doesn't have the structural strength that plywood offers plus the wind catches it hard.
The green mesh is easy to work with, is suficiantly solid to identify shoot throughs and obscure the targets but is easier for the the RO to clear the range as you can still see through it. Its light and stands up to the elements very well and looks the best over time. Well worth the expense IMO