First, please note that it is somewhat dangerous to lump all people in a given region together and to assign them one "character." Any discussion of regions' characters is necessarily a generalization.
It is generally said that the character of New England was much more sober and egalitarian than the Southern character. The character of the South was more aristocratic, flamboyant, and hierarchical. This is said to have come about because of the plantation economy of the South on the one hand and the Puritan ethos of New England on the other.
Southern culture was dominated by plantation owners who saw themselves as a natural elite. They acted like European lords, displaying their wealth and their status for all to see. By contrast, New England's culture came from Puritans. These were people who felt that they needed to act in a godly way so as to set an example for others. They were also people who believed in humility and in treating other men (at least) as equals.
Because the two regions were settled in such different ways, they came to have (generally speaking) very different characters.