I assume that this question is asking why the southern colonies were better than the Middle Colonies or New England for agriculture. Agriculture is the only way in which the southern colonies were clearly better than the other two regions.
Climate and soil were the two main reasons that the southern colonies were better suited to agriculture than the other colonies. New England had a cold climate and poor soil. The Middle Colonies did have good soil and strong agricultural economies. However, their agriculture was not as productive as the southern colonies’ because their climate was not as good.
The southern colonies had very rich soil. They also had a much warmer climate than the other regions because they were farther south. Because their climate was so mild, their growing season was longer and farms there could be more productive. This is why they were better than the other regions in terms of agriculture.