Self-checkout seems better to me, because it decreases monotonous and forced public interaction (thus somewhat automated anyway): Beep. Beep. Beep. Do you want loyalty points? That's 21.46€. Do you want the receipt? Goodbye! Beep. Beep. Beep...
It uses less space.
It is parallel instead of serial.
The work is not much more than putting groceries on a checkout lane anyway, except for unlabelled fruits and vegetables.
Self-checkout allows for smaller stores and coops, for example in villages or as kiosk.