Comment Real advantage is the assist, not the braking. (Score 1) 12
For the best hybrids, the major advantage is not the regenerative braking. While that helps save some energy, it is relatively minor.
Instead the main advantage is that you can design the internal combustion engine (ICE) to run at a consistent RPM. You do not need to run the ICE at different speeds to get 30 mph, 45 mph and 60 mph. Instead you have one that just runs at a set RPM. Then you use the hybrid battery to supply all the power at low speeds and a boost at the max speeds.
The more efficient ICE can add 10 more mpg to an engine alone, without even considering the regenerative braking.