Aloha!
Kauai is magical. It’s a very small island that has a lot to offer. Most visitors fall in love with Kauai and keep returning regularly because of its beauty and aloha.
One of the most frequently asked questions is, “On which side of the island should I stay?”
The easy answer is thatyou can’t go wrong anywhwere.
The tough answer is that it depends.
It is not too simple because it depends on multiple factors such as budget, length of stay, season, and if it’s your first trip to Kauai. I am a frequent traveler to Kauai and a vacation rental owner on the South Shore of the Island. This is how I would visit Kauai:

1- Winter: October through April:
I would stay in the South Shore so I can get as many sunny days as possible and keep an eye on the weather for a day trip or two up North. If you are a big time surfer, the North Shore is your spot although you can still have good surfing in Poipu.
Winter is also great to see whales and they are there mid December to end of March. If you are lucky, you can see some in April.

2- Summer: May through September:
Ideally, I would prefer to split my time 60% South, 40% North. If you are staying more than 6 nights in Kauai, split your stay between between both sides as suggested. The beaches up north are mesmerizing and it’s a must to spend time there. However, it is more expensive and it’s quite remote to visit other parts of the island.
If you are on a budget, staying at two rental properties could be a bit challenging because you will be charged twice for the clenaing fee but I think it is worth it.
Make sure you stay at a vacation rental that provides you with beach chairs, umbrellas and snorkel gear, and it will make up for the cleaning fees. There are also great options in Kapaa and you can still visit the South and North but you will be spending a lot of time driving as traffic gets hectic.
Duration of your stay:
If you’re a first time visitor, I highly recommend spending at least 8 nights in Kauai and staying in both the North and South sides of the island. If that’s not a possibility, pick an area based on your preferred activities and you will be happy either way.