Hawaii and the Caribbean have a few basics in common; sand, water, beaches, and hotels. But they are vastly different! Depending on the Hawaiian island you choose you can find volcanoes, lava flows, BLACK sand beaches, mountain hiking, and Waimea canyon (a 10 mile long, 1 mile wide and 3500 foot deep canyon), and a vast range of cultures.
Hawaii is definitely worth the trip. Each island offers something different and Aloha airlines makes it fairly easy and inexpensive to day trip from one to another.
I've been to both multiple times and although the Caribbean is easier and usually less expensive to get to I would choose Hawaii and recommend at least one trip there for everyone!