Pressboard material is lighter weight, easier to damage, will swell and explode from water, but it costs less. Plywood is heavier and meant to withstand more abuse. Now there are companies that offer a combination of both, where the floor, back and shelves are pressboard, but sides that are exposed, drawers and fronts are wood, this is a popular option a lot of people consider, because the areas that get the most abuse are wood but the remainder are pressboard keeping costs down?