Question What's better? The 7800x3d or the 7-13700K?

Just being pedantic here but modeling and rendering are not the same thing, back in the days you would model on one system and send the final files to a render farm, or render box, to be rendered.
I doubt that the 7800x3d would be noticeable different in the modeling part alone.
But yeah if rendering is a concern the 14700k will be better, just make sure to not allow the mobo to apply a completely crazy overclock automatically.