Hawai'i or The Big Island
The Big Island is BIG at 4,028 square miles with 266 miles of coastline. While it has over 60% of the land area in the in the six major Islands, it's population is only 185,079. It is also the home of 5 major volcanoes, Mauna Kea (white mountain), Mauna Loa (long mountain) Kilauea (at the heart of the 330,000 acre Volcanoes National Park), Hualalai, and the oldest volcano, Kohala, which may be a million years old. The hot spot that formed the Island chain from Kure to the Big Island is still under Kilauea, and it has been creating lava flows for the last 32 years. The main crater Halemaumau is 8 miles across and 740 feet deep. The main vent is Pu'u'O'o, but Madam Pele is venting her wrath from other points too. The Lo'ihi Seamount, about 15 miles south of Kilauea is about 3000m high, but still considerably below the surface, so don't expect to vacation there any time soon. Dormant volcanoes include Mauna Loa and Hualalai. The Four Seasons Resorts are hoping that Hualalai stays asleep, since they have a beautiful Resort that would probably not survive an eruption. Mauna Kea, at 13,796 feet is the tallest mountain in the Pacific.
The BI, like all of the Hawaiian Islands, is green and wet on the North and East side and arid on the South and West. This is because the Trade Winds, travel across thousands of miles of ocean collecting moisture, and when they hit a volcano, rise, and cool off, dropping rain, which form rivers. The Hamakua Coast is typical of that process. Rich vegetation covers the slopes of Mauna Kea from Hilo to the Waipio Valley. Beaches are mostly volcanic sand that can be the color of just about any oxide. It depends on what the volcanoes are producing. The best coral beaches are on the Northwest side around Waikoloa. South Point is the southern most point in the US and it has some wild natural beaches. If you want a non-tourist experience, that is a good place to visit. The Parker Ranch is a working cattle ranch and is a the largest in the US. If you want a Paniolo (cowboy) adventure, that is the place to go. If you are visiting the BI, make sure that you leave enough time to visit the Volcanoes National Park. Just describing it would take more space than is available here.
My advice is that you use the Kona (KOA) airport, but there is another airport in Hilo. If you don't like crowds, this is the place to go, but don't go the week of the Ironman.