I think the physics are different, a ball is basically a car without a differential, so it's going to behave differently on the tracks. I'd imagine the ball is harder to simulate because of that.
One of the results for hilbert curve marble tracks, mentioned elsewhere in the thread, was a video showing how to make one in blender, which has a physics engine so it can simulate it pretty well.
But for hobby purposes I would suggest to contact some university, they have such software, and they could find simulation of balls motion at marble fountain interesting for research (and educational) purposes.
