The rate of cooling of an object varies and slows as that object approaches the temperature of the cooling source. The experiment should start with identical masses of water in identical containers and engineering to prevent evaporation (a plastic film will do). Because of the higher temperature differential between the hot water and the cold water, the hot water will initially cool faster than the cold water. As the hot and cold water cools to closer to the source temperature, both of their rates of cooling will slow. However, at a given point, the hot water will reach the starting temperature of the cold water. At the point it reaches the starting temperature of the cold water, it will have the same temperature differential and therefore the same rate of cooling with which the cold water started. It will also take the same amount of time for the "hot" water to freeze from the temperature at which the cold water started. Because of the length of time that expired for the hot water to cool to the starting temperature of the cold water, it will always take longer for the hot water to cool. That's physics.