You forget, the regenerative bike is faster and lighter, making it to the top of the hill first, leaving the non-regenerative bike with heavy battery far behind. So the rider has a much deserved resting period while he coast down hill in regenerative mode. Once reaching bottom of the hill, the rider is fully recharged, able to extend the lead even more.
I know from experience in gearing, closer matched gearing allows shifting down to more efficient pedal rate upon increased road grade. Wider spacing means dropping down more in term of speed, so closer gearing means faster recovery to top speed when road grade is restored.