The 20" is 7 rounds +1 in the tube....I actually have both the 18.5" and the 20"....both are fine shotguns, both are good for HD, usually i would think you don't need 2 extra shots, unles planning on a zombie invasion, but what the heck...why not? Basically, go with ever your most comfortable and happy with. -BamaXD (a happy Mossberg owner)