Regen braking is not actually via braking. The system regenerates via motor/generator when power is not in demand.
Braking is the best form of stopping, however, the B mode is just like shifting from 4th to 2nd in a manual car, plus this mode does charge battery by reversing direction of motor to charge battery.
When battery is fully charged, the system knows this and does not apply regen. If battery was overcharged it would possibly explode.
It is cheaper to replace brake pads opposed to transmission. Normal brake pads are also standard fit.