We're fairly experienced independent travelers, but have mostly driven everywhere. Island-hopping in the Cyclades in April will be something new for us but we haven't found any information about whether it's impractical or not to take a rental car with us, or to allow the extra time and hassle(?)to rent one on each island. Our tentative itinerary includes from Athens (Peraeus): Crete, Mykonos, Santorini, Paros & Naxos.
I can't think of any benefit to having a rental car for an entire island-hopping vacation. Depending on how much time you have on each island, you can rent a car for a day or two. There's no hassle; just stop by a rental agency and pick one up, then return it when you're done. The rest of the time, you'll be on foot or using public transportation, which I think gives you a totally different experience than being in a car. Plus, the car rental for your entire trip will be costly; your ferry tickets will be more expensive with a car; you will not be able to choose just any ferry (not all ferries carry cars); and if it's a busy route, and busy time of year, you may need an advance reservation for your car ... whereas if you're just walking on, you can pick virtually any ferry and need no reservations.
I agree. It's not practical to take a rental car with you. It's expensive. Also, rental cars are easily found on each island, often right at the port or just a short walk away. Be sure to go to your local AAA office to pick up an International Driving Permit, no test or membership required, for $15 plus a photo fee if you don't bring 2 passport photos with you.