What are the differences between the Canon EF 50mm f/1.8 STM and the Canon EF 50mm f/1.8 II lenses?

The Canon EF 50mm f/1.8 STM lens has a newer design with smoother and quieter autofocus, while the Canon EF 50mm f/1.8 II lens has an older autofocus system that is noisier. The STM lens also has better image quality and build quality compared to the II lens.