We book through the cruise ship (only so that the ship wouldn't leave without us!). But, I highly recommend the Hawaii Volcanoes National Park Tour. You actually get to walk on 'fresh' lava. You can also see the black sand beaches. Expensive, but worth it.
If you're talking about Tom Barefoot's cashback tours, they are the best. They take you places and offer things that the rich and famous go to Hawaii for, the beaches, sailing and watersports. If you're just going to do the normal tourist thing like see extinct volcanoes,see steam coming out of cracks in the ground, look at plants or visit memorials and museums, the ship's tours are fine. If you want to see the real Hawaii, you need to get away from the tourist traps and Tom's will do that.