There's no real reason to visit industrial León, 56km west of Guanajuato, but due to its importance as a main bus hub within the state of Guanajuato you may well have to change buses here. Also, it's only 20km from Aeropuerto Internacional de Guanajuato. It's unlikely you'll need to stay here; bus connections are plentiful.
If you want to fill an hour or two before a bus connection, it's worth wandering the streets surrounding the bus terminal, known as Zona Piel (Leather District). León has a long history of supplying goods: in the 16th century it was the center of Mexico's ranching district, providing meat for the mining towns and processing hides.