2S vs 3S run times?

[GO-RIDE.com]

For conversations sake, let's say I used my above example except that:

1. I optimized each motor for the voltage of the battery and thus used the same pinion for each setup to reach my 35mph top speed.
2. As stated before I would drive each car the same pace around the track.

Would this allow the 3100 3s to have as long, or nearly as long, of a run time as the 4200 2s?