I think this is a good minimum time for a trip, although 10-14 days is better if you want to visit multiple islands. Some visitors do visit Hawaii for 4-5 days, but it's a long way from the US mainland (or anywhere!) for a short trip, and you'll spend the first few days adjusting to the time zone change.
Is 4 days enough in Maui?
If you plan in advance, you can see a lot in 4 days in Maui. The guide below takes you from historic towns in West Maui and pristine beaches on the southern coast to scenic drives that wrap around rainforests and dramatic cliffs on the remote eastern tip of the island.
Is Maui or Kauai more beautiful?
Regarding dramatic Hawaiian scenery, Maui and Kauai are both exactly what most travelers imagine. Stunning coastlines, towering mountains, and lush jungles abound on both islands. However, the main difference between the two islands comes down to the variety in the landscapes, which Maui wins by a narrow margin.