Hey,
I have traveled both ways, travelling with my boards and renting boards once i get there. It really depends on if there is a reputable place to rent, what it costs, and what kind of boards are available to you.
For Oahu, you can't go wrong with renting. There are lots of options, the best I have found is
www.hawaiisurfboardrentals.com. Check out the site, they have a nice board selection, their rates are great, for a 10 day trip its less than $200 bucks, and you don't have to worry about your boards not making it or getting beat up by careless air handlers.
I am actually going ot Oahu on Friday and already have my board reserved. They will also swap our your board for you and deliver and pick up the board to where ever you are staying.
It beats paying the United Airlines rate of $175 each way per board!
Hope this helps!