Thea Render looks to have tight integrations with C4D. You might have noticed that there are no shortages of third party plugin-renderers these days, especially for Cinema 4D.
There are figuratively tons to choose from — from V-Ray, Arnold, Octane, Mental Ray to even a port of Blender’s Cycles renderer.
One more you can add to that list is The Render. Thea Render is an interesting animal in the render world. It is both a biased and unbiased renderer.
Further to that, Thea has an interactive renderer called Presto, that can run both on the CPU and the GPU.
Thea also has some interesting Cinema 4D integrations. Interactive render regions are supported in C4D, but Thea also has its own integrated darkroom, Material Lab, support for instancing, and texture baking.
Thea for C4D comes with the plugin interface, and Thea Studio, a stand-alone application for further scene staging and material/lighting tweaking.