Big Island or Kauai
 

My husband and I are going on a semi-belated honeymoon. 5 nights on Oahu and another 5 on either Kauai or The Big island. I can't decide which. I have been to Oahu and Maui but not to the other 2 islands so I don't know which is the better choice. My husband has never been to Hawaii. We are both late-twenties, love culture, adventure, food, drinking, music, etc. Beaches are nice, but I can't just sit on a beach without getting antsy. I want to be sure there there is more to do than just that. I also don't want to be completely isolated. Might be nice to have a mix of adventure-seeking during the day and good nightlife if possible. We are going in mid-late September and I read somewhere the Big island is unbearably hot at that time. Any input would be appreciated. Thanks! :)

Since you've already been to Oahu, why not go to the Big Island and Kauai this trip? They are very different and would make a nice contrast.

Big Island is quite different than Kauai. Love them both but for different reasons. BI is very volcanic and the lushness is down by the beaches where the hotels and resorts are usually located and over toward Hilo. Hilo is the wet side of the island and probably got a good hit from the last hurricane that came thru so I would check on that before heading there if that was in your plans. BI is BIG! The active Volcano is very interesting as is the whole nature center there. Hiking, kayaking, swimming, snorkeling, etc. but if you are looking for tropical greenery than that is probably not the place for you. Kauai is lush and very tropical. My favorite of them all. There is hiking, snorkeling, tubing, bike riding, surfing, etc to keep one occupied. North shore is more rural perhaps and some great beaches along the way. Love the funky town of Hanalei and Hanalei beach park is wonderful as is Ke'e beach at the end of the road. Poipu is more touristy perhaps but lots of adventures there as well. Both are great. Staying in South Shore and driving to Northshore can take about an hour or more depending on traffic.

I like Kauai but I love the diversity of the Big Island. That would be my pick.

I "like" the BI. I "LOVE" Kauai.
My niece and nephew honeymooned in Maui and loved it. Then they came to my wedding on Kauai and said they'd never go back to Maui; that Kauai is so much more beautiful--and has so much more to do.
Kauai gets my vote--but as you're seeing, it's a matter of opinion.

I have the same reaction to Maui vs Kauai. For me Maui is very similar to southern California but Kauai is more tropical and lush and more like I would imagine Hawaii was like back in the 50's before it became built up. Kauai still has that feel.

Been to all the islands. Go yearly to Kauai and have been going for last 22 years. Kauai gets my vote. Not too touristy like Oahu and Maui....Big Island is a nice contrast but not very lush and lots of volcanic rock. Some nice beaches but still prefer Kauai.

IMO, Kauai offers the best of Hawaii sights and activities on land, whereas the Big Island is best in the state in and under the water. Together I think they make a perfect trip. But if you're sticking with Oahu, BI offers more of a contrast than does Kauai, so I'd go with that.

With 5 days I'd go to Kauai, Big Island really needs more time, went there once for 5 days and only saw a handful of things. Both are beautiful but you need 7-10 days for Big Island.

Five nights is too little for Big Island if you want to see both sides: Kohala Coast and Volcano. September is Hawaii's hottest month and feels extra-hot on the bare volcanic rock portions of Big Island (west side). If the volcano is active...even worse, hot AND vog.

September is still nice on Kauai's most gorgeous northern shores, although the ocean will have started to turn to calmer south. Poipu has a bit more touristy stuff to do.

Neither of these islands has anything like the man-made choices Honolulu or Maui's more developed areas.

Since it will all be new to your DH, maybe Oahu + Maui would be the best fit. If you've stayed West Maui before, maybe choose South Maui this trip -- or the opposite.

Better get your rental car(s) reserved!

I agree with Jamie. Save the BI for a longer trip.