I'm migrating from XNA to SharpDX in Win8. I noticed this
DrawBitmap call in one of the samples.
Is this different in some shape, way or form from XNA's
Yes, they are absolutely different.
The SharpDX method you linked to is a wrapper around the native Direct2D
DrawBitmap methods; SharpDX is primarily just an interoperability API that provides a wrapper around native functions (excluding it's "toolkit" APIs).
SpriteBatch is a high-level wrapper around Direct3D drawing primitives (vertex buffers, textures, shaders) that provides an easy way to draw sprites.
You can use both interfaces to draw 2D sprites on a screen. Used properly you can probably achieve performance parity. However, they are not interchangeable interfaces.