First of all a question. How many gun fights are you planning on being in? When I see people putting up multiple thousands of rounds of self-defense ammo, I ponder the same question.
Most of us hope and pray to never be involved a gun fight! However, it can happen. What's the difference in being prepared by having ~15 rounds of 12 ga. on your shotgun vs. 15+ rounds (and extra mag) in your semi-auto handgun?