Subdivision vs no subdivision (rollover image)
A native C4D Subdivision Surface object is translated to Arnold subdivision by default instead of exporting the tessellated geometry. This is because subdivision in render time is much more efficient, allowing the renderer to make extra optimizations.
In However in some cases you don't want to use Arnold's subdivision but simply export the final subdivided geometry from C4D. For example, if you use deformers under the Subdivision Surface object. To export the tessellated geometry you have to add an Arnold Parameters tag to the Subdivision Surface object (C4DtoA Tags > Arnold Parameters) and enable Export tessellated geometry.