The difference is price is from high quality wads (flight control is hard to beat) and composition of the shot. Basic buckshot uses unplated soft lead shot. The patterns can be erratic because the shot get severly deformed when fired. Hard shot improves patterning. Copper plated or even nickle plated shot is best as the shot remains very round when fired. The difference between soft shot-fiber wads and plated shot and patten control wads is night and day. The difference can be 50% better patterns and 2X the price. They can make the difference between 100% hits in a HD situation and one or more fliers bouncing around inside your home.
In life, strive to take the high road....It offers a better field of fire.
"Robo is right" Fuzzball
Realistically anything in 12 gauge be it high or low brass at home defense ranges is very potent medicine! In most homes it would be difficult to get say more than 30' and 10' to 15 is more likely.
So basically in my opinion your over thinking this, any 12 gauge round inside your home is more than enough to stop any attack.