If you plan to travel between Split and Dubrovnik, I really recommend doing via bus. The bus ride is along the coast so you get stunning sea views along the way. The bus is also the cheapest way between Split and Dubrovnik and bus services are very frequent. One way ticket is about 110 kuna (15 Euro) while the round trip is 176 kuna (23 Euro).
yes, the views of the sea are spectacular, but be aware that the journey takes 5 hours. Car transfer maybe more comfortable, though it's really expensive (between 200 - 260 EUR depending on the number of people).