Each buckshot pellet shares a reduced portion of the entire load's energy.
Rapid energy loss occurs through ejecta and poor coefficients.
Stopping power is a legitimate concern, as multiple pellet hits IS a requirement to achieve fast stops.
Aim is a must, and there must be control of the entire payload through proper choke/load combination. Testing.

Sectional density and available energy of a soft lead round ball/plated shot compared to a well designed rifle bullet, big differences.
Dependable, powerful results on target. Rifle.

Inside the house, I want the fight stopped as fast as possible.