I would not dismiss any rifle. But I do have preferences.
I think an 8 round capacity in a 12 gauge shotgun is accepted because that's about all one is going to get in a practical package. Any magazine more than that requires heavy, large boxes or drums that most guys find objectionable to carry and use. Also bear in mind that each round of shotgun ammo unleashes multiple projectiles (except for slugs, of course). Eight rounds of 00 buck dispenses 72 projectiles. I think in most situations 8 rounds will solve the problem unless one is in combat on the battlefield. In that case, call in armor support and an air strike.