Hilo is a decent port with fairly easy access to the rental car booths at the airport. You can't really walk anywhere so you either take an excursion or get on a rental car shuttle. Proximity to Volcanoes National Park makes this a favorite stop.
Like Lahaina, you tender to this port. Renting a car can be expensive if you reserve one at the King Kamehameha hotel, or time consuming if you take a shuttle to the airport because it is seven miles away.
Kona is a nice town to walk through and has some unique shops and restaurants.