Well first things first, the language itself, Tamil, Telugu, Kannada, and Malayalam, are pretty much different from each other. Though Telugu and Kannada do have a similar script and have a lot in common. Again Tamil and Malayalam, have many features in common, but both of them are markedly different from Telugu or Kannada. And I have not yet added Tulu, Konkani, Kodava to the mix. In fact, neither of these states are homogenous either. The culture in Rayalaseema or Telangana is quite different from Coastal Andhra. North Karnataka is culturally different from the old Mysore region, and Coastal Canara is more similar to Kerala. Again in Kerala, the North and South regions are worlds apart, while there are significant differences between Kongu Nadu( Coimbatore, Salem, Erode) and Southern Tamil Nadu( Madurai and surrounding areas). And you have Coorg which is a totally different world. It also reflects somewhat in the festivals too, Andhra Pradesh and Karnataka follow the Shalivahana Saka calendar, while Tamil Nadu and Kerala have their own regional calendars. While they follow the same naming system for months, AP and Karnataka follow a lunar calendar, while Tamil Nadu and Kerala have a solar calendar. So while Ugadi is celebrated as the New Year for both Andhra Pradesh and Karnataka at the same time, Tamil Nadu and Kerala, observe their new years Puthandu and Vishu, a few weeks later, and both falling at the same time. Again Ganesh Puja is a major festival in Andhra Pradesh, Karnataka, and Tamil Nadu, but it is not that big an occassion in Kerala. Sankranthi though is commonly observed in all 4 states, with some slight variations here and there. The marriages are different too, in the 4 states, with Andhra and Karnataka having slightly elaborate ceremonies, and again it differs based on the community and region. Here are some pictures of a traditional wedding from the 4 states, each of them are different.
