I've heard that for every pound of unsprung weight you can remove (wheels, tires, etc) its like removing ~3 lbs of weight from the vehicle. But you know what people say.
It makes some sense though. Yes, you can coast further with a steel wheel since you have a higher polar moment of inertia. But you paid for that when you fought it while putting in power to accelerate, and since both in and out have frictional losses and other inefficiencies, the lighter the wheel the better. QED.
In an engine you have a flywheel; same concept but in this case you need it to smooth out the harsh peaks that come from piston compression and the resulting explosions.
IOW: go with the lighter wheels esp if the D is the same. Think about getting some cheap alloys.
