He explained it in the comment: "there's less vertex data to generate and pass to the GPU"
This is false. If you're drawing a quad, you pass 4 vertices. If you draw 2 triangles forming a quad, you also pass 4 vertices (using a triangle strip and index buffer). The index buffer is not updated every frame, just once.
On Windows, the GPU is driven by either DirectX or OpenGL. Native OpenGL ES drivers for Windows are ONLY needed for cross-platform development where applications destined for mobile devices are built and tested on Windows first.
That's a really good reason to have native OpenGL ES drivers IMHO. But why would you create an app on windows, and release it on any platform except windows?
We have a equal opportunity Calculus class -- it's fully integrated.