I love the islands of hawaii, they are beautiful, lush, and serene, and the aloha spirit is alive and well. If I lived in California, I would go every year.
That being said, the reality is i live in chicago and flights are twice as long and nearly twice as much, but the main reason is: As much as I love the hawaiian islands (I learned to swim in Maui as a child), the fact is that it is part of the US, and it sure feels that way when you are there (like one big California convention!) That is the main reason I choose to go to the Caribbean more often, because I enjoy the more diverse feel and different cultures of the different islands.
Now comparing beauty, its a tough call depending what Caribbean island you are comparing, some are prettier islands than others (think st lucia compared to aruba). As for beaches, i think the white and pink sand beaches and clear carribbean water are prettier than hawaiis golden sands and blue pacific waters (there are also unique green and black sand beaches) but beauty is in the eye of the beholder. Of course the Caribbean has the reef and is far superior for divers and snorkelers alike ( think cozumel, cayman islands, curacao). Hawaiian sunset is something special.
People on the west envy the east for proximity to nyc, florida and caribbean, people on the east envy the west for proximity to vegas, cali, and hawaii. Grass is always greener ....