My wife and I are planning on spending two weeks in Croatia this June, starting out in Dubrovnik and flying out of Venice. We'd like to see either or both Korcula and Hvar and then make our way northward. The question is, with a car, whats the best way to do that? Which route? Do we bring our rental on a ferry to the islands or leave it in one of the ports on the mainland and do public transport on the islands? Also is it possible to do a day trip from Korcula or Hvar into Split? I know, lots of questions, but I'm very early in the planning/research process and I'm trying to figure out whats a way to do this without a whole lot of back tracking and swapping rental cars.
Not taking a car to the islands will give you a greater flexibility on hopping between them. The car ferries are fewer and much slower than the catamarans. If you plan to drive around the islands and have the time to wait on the car ferry, feel free to drive. However, if you will really only be spending your time in the main towns, you should be fine without a car.
A day trip to Split will be easier from Hvar than Korcula. There are regular ferries back and forth between Hvar and Split. Often people do just the opposite (a day trip to Hvar from Split). Korcula is about 2 hours away from Split by catamaran. And once you factor in the frequency of the ferries between Korcula and Split, you may not have a lot of time in Split if you tried the day trip from Korcula.