The "Big Island" is different, in my mind, a lot of it is very desolate, just black and brown rock as far as one can see. Parts are tropical rain forest. Parts are resorts (mostly on the western side). A good portion is cattle and horse ranches, it looks like Texas. My wife likes it a lot, unfortunately.
The beaches, in my view, are not that great. The sand is brownish and coarse, there can be rock outcroppings that can skin your feet. Some are quite pretty, palm trees and whatnot, some have pools just inland. The resorts are quite nice.
We usually drive to Volcano NP when we're there, of late not much has been happening though. Chain of Craters road is interesting.