The shotgun is without a doubt the best gun for people with limited firearms experience. It is simple to operate and does not require refined marksmanship skills to hit with. Plus, while it will penetrate drywall, a buckshot load will generally not go through multiple walls and end up in your neghbor's house--a significant issue in an urban setting. I assume you're in a city. The 20 ga. is a superb choice--less recoil than a 12. Self-defense 20 ga. ammo can be hard to find, though, so check your area for supply before you buy a gun. Bottom line, your training will make more difference than your equipment. People seldom rise to an occasion, rather, they fall down to the level of their training.