conceptual question

I'm assuming these cubes are not ice cubes since you didn't call them ice cubes. Both would experience the same rate of temperature drop. The smaller one would cool more quickly, as there is less to be cooled. The smaller cube would have a cooler distribution. The middle of the smaller cube would be cooler. I would assume that this would make the smaller cube cooler by the end of a certain time, as the middle of the larger cube would not have cooled as much due to the amount of the cube that the water has to cool. If you are talking about an ice cube, this situation would be completely different.