To find the area of the square plot, we can use the formula A = s^2, where s is the length of a side. In this case, the side length is 60 m, so the area of the square plot is 60^2 = 3600 m^2.

To find the area of the rectangular plot, we can use the formula A = l * w, where l is the length and w is the width. We are given that the width is 1.5 dam, which is equivalent to 15 m. Since the perimeter is the same for both plots, we can find the length of the rectangular plot by dividing the perimeter by 2 and subtracting the width. The perimeter of the square plot is 4 * 60 = 240 m. Therefore, the length of the rectangular plot is (240/2) - 15 = 105 m.

The area of the rectangular plot is then 105 * 15 = 1575 m^2.

To find the difference in area between the two plots, we subtract the area of the square plot from the area of the rectangular plot: 1575 - 3600 = -2025 m^2.

Therefore, the square plot has a greater area than the rectangular plot by 2025 m^2.