Having Smooth on by default makes the most sense, especially since it takes Auto Smooth into account, and you're more likely to want a smooth surface than a faceted one. (I looked through my apartment and couldn't find any object with curved faceted surfaces, they all are "smooth" )
Windows 10 Pro - AMD Ryzen 7 2100X 8 core 3.70GHz - 32GB RAM - GeForce GTX 1080 8GB Octane Prime - Blender Plugin user