Brushes are generally meant for prototyping layouts and for constructing very simple environments. They don’t perform we when scaling up to high-polygon environments.
Static meshes are the recommended primitive for building larger and more detailed environments. The levels in Infinity Blade and Gears of War are nearly 100% static meshes. Of course, the downside is that building a level with static meshes requires a large library of meshes or a significant effort modeling and UV mapping them in an external tool like 3D Studio Max, Maya, or Blender.