It’s a bit like the difference between the North Island and South Island in NZ. Or Eastern and Western Europe. India has an arbitrary border somewhere in the middle; what lies to the north is designated as North India, while everything south is considered to be South India. Yeah, there are differences, but should we really be that bothered?
Living as I do in Kerala, I have picked up many more arguments for the South than the North. For example: The North is dirty; the South is clean. The North is more poverty-stricken; the South is more affluent. The North is more illiterate; the South is more educated. The North is corrupt; the South is… less corrupt. On the flip side: the North is more liberal and varied; the South is more conservative and uniform. The North is more cultured; the South less so.