Tough call, it's between the AR and shottie
Ammo for the AR and shottie are plentiful and cheap.
shotgun shells can be had at Walmart and Meijer tho, they don't sell .223/5.56 either place
AR's mag capacity is 5-6 times that of a shottie.
Shotgun has to be semi-auto, the one in the pic appears to be just that.
Shottie is better for large game (i.e. deer, elk, moose, bear)
AR is better for long shots
Both will put holes in your house, your neighbor's crib, and might hit the car next door
Still gotta think about it.