Which is Better for Kayak Fishing, Big Island of Hawaii or Kauai?

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I have been to both but have fished neither. A friend just told me about renting a house on Kauai next summer and kayak fishing.

I was wondering if the Big Island would be a better choice for kayak fishing? Say out of the Hilo area? Where is the best place to rent fishing kayaks?

I am really considering doing this as well as my wife seems very open to the idea of going to Hawaii again.