I couldn't help but notice that the 590 has a higher capacity.
https://www.classicfirearms.com/mossberg-590-shockwave-12ga-pump-50659/
https://www.classicfirearms.com/remington-870-express-12-guage-14-inch-barrel-raptor-pistol-grip/
https://www.classicfirearms.com/mossberg-590-shockwave-12ga-pump-50659/
https://www.classicfirearms.com/remington-870-express-12-guage-14-inch-barrel-raptor-pistol-grip/