My wife and I visited Oahu, Kaua'i, and Maui on our honeymoon, and would go back to Kaua'i in a heartbeat. We loved the people, the natural beauty, and the laid back atmosphere. It's fantastic.
My wife and I were just in Hawaii a couple months back and we spent 4 nights in Waikiki on Oahu. Which was a lot of fun and a lot of night life and good Restaurants? Also enjoyed Kona Brewing Company?s beer.
We also spent another 6 nights in Kaanapali on Maui, quite a bit of difference it was a lot more laid back. Driving around the island is interesting as most of the roads are very scenic and winding. But most of the time you have to come back out the way you came in. Just up the road from Kaanapali, there was the Maui Brewing company. They had a good selection of beer. And I really enjoyed there Coconut Porter.
Go to Kaui or Maui they are already too crowded with tourists a few more won't make a differance. HA HA HA naa naa only joking all the islands are awesome to see. Pick anyone and you'll be happy you can't go wrong with any one, just be polite to the locals, slow down abit and relax, you'll enjoy your trip more.