If high school physics serves me correctly, the amount of energy in the 4s 5000mah battery is 4X3.7V X 5A X 1H = 74 Joules. The amount of energy in the 5s is 5X3.7V X5A X 1H = 92.5 Joules.
If you motor and gear the cars to run at the same speeds, you will get more runtime out of the 5S pack.
Otherwise, you might get less "runtime" but cover more distance (for example, number of laps) within that period of "runtime". Is distance important to you?