Not quite.... the unsprung mass does help but it is marginal, lighter wheels accelarate and decelarate much easier. You can take the flywheel off an engine and it will NOT affect kW or Nm! Putting a lighter crank on a bicycle does not increase the riders wattage... a heavier flywheel makes the car more drivable due to its momentum, more difficult to stall but a at a tradeoff as rpm will rise and drop slower as well as a bigger chance of locking up the driving wheels on a downshift. At a constant rpm this weight will have no effect. When it comes to laptimes etc the rule of thumb on a racecar: every kg rotating mass saved =4kg static mass. If the bicycle had to accelarate a couple of times the lighter wheels would help, at constant speed they will not.
