The idea of one group of colonies being better than another is entirely subjective. In other words, different people may view each group of colonies as being "better" than the others for different reasons. Ultimately, whether you place the southern colonies above the northern ones depends on what metric you're considering and what group of people you're referencing.

If we look at your question in terms of economic strength, then you might conclude that the southern colonies were stronger than their northern counterparts. The southern colonies grew cash crops like cotton, tobacco, and rice. The huge demand for these crops helped some farmers grow extremely wealthy. Plantations began to rise across the region, which helped the farmers earn even more money. In this way, the southern colonies probably were better for rich white farmers.

However, somebody had to work on those plantations. At first, the plantation owners used indentured servitude to find the workers they needed. This typically involved a plantation owner paying for a worker's trip to America in exchange for seven to ten years of free labor. There were some initial successes with this system, but indentured servants were treated poorly in a variety of ways. They eventually rose up in Bacon's Rebellion, which was the first rebellion in the history of the United States, occurring in 1676.

Bacon's Rebellion facilitated the southern colonies' shift toward using slave labor for their plantations. While the rich white plantation owners continued to earn gobs of money, they did so on the backs of slave labor. Of course, the southern colonies were definitely not better for the slaves.

Although northern colonists were at first interested in replicating the south's farming economy, they found their soil was not good enough to do so. This led to the development of trades like fishing, sailing, and merchanting, among others. The northern colonies had a larger middle class, which was better represented in the region's political processes. In this way, the northern colonies were likely a much better place to live for individuals who weren't part of the economic elite.

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.