The answer depends on your budget and your time. If you have enough time and can afford the longer option, you are surely recommended to book 2 night cruise. Some of the listed reasons are as follows:
- You will have more time to spend on boat and feel less rushed about the road travel between Hanoi and Halong Bay. Many travelers who cite their only discomfort with taking a 2 day trip is that, they have to do 4 hour road trip on both first and second day of the trip.
- A 2 night trip will allow you to explore further parts of the Bay such as Lan Ha Bay, Bai Tu Long Bay, Cat Ba Island and experience different activities like swimming, kayaking, boat rowing, trekking (in Cat Ba National Park), etc. that a 1 night cruise cannot otherwise offer
Most cruises use a day boat on their second day program, which will be able to take you to the more secluded caves and beaches in Halong Bay. There will be longer time for kayaking and swimming as well.