Since I model small trains in addition to military miniatures I am familiar with many of Woodland Scenics' products. They have quite a range of supplies and materials.
One advantage of WS is cost - they are in mass-market so they will often cost less than the materials for H&A or B-A-R. On the other hand they are often not as "fine" as the other stuff. One can certainly use them together and have great results. WS has trees that are good for "backgrounds" and they have their "premium tree" line that are very fine and look nice in the foreground (but are more pricey). They have all kinds of ground foam products in multiple sizes and colors that are available in various size packages. They make a nice "snow" also.
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