Parthius, the subpatch is merely a simplified grid of polygons and control points superimposed over a dense mesh to make modeling easier. How dense the mesh actually is at any time can be adjusted depending the user's preference. If you want more detail in your subpatched model, you can add more control point. Though finer detail might be produced with the ultra-dense meshes of Zbrush, most people would find it more useful to create that sort of detail with texture map displacements. Memory limits are a very real issue in 3D if you're building complex scenes, but the point is that the actual geometry isn't "minimized" by a subpatch.

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