There is a section of people who believe that adolescence years are the joyful times of the lives. This concept could be true as the minors do not have the responsibility of bringing food to the table. To its contrast, I go with the second option of taking adult life as more contented despite the load of responsibilities.
The age of teens is certainly of less responsibilities and more of school life and hanging out with friends. Thus, they enjoy their time with their peers, play games together, and focus on studies. As for example, schoolchildren of some schools in India, get summer, winter break with multiple other holidays which gives them abundance of time to spend with their friends and family.
Whereas, I personally believe as an adult, one gets a sense of freedom and independence with the responsibilities. A grown up person has learnt lessons from his early years and develops the adaptability towards uncertain life situations. As a result, they live their lives with satisfaction of a settled career and a family. For instance, a family man is definitely considered much more ecstatic than the young ones who are trying to figure out lives, as per some newspaper statistics,
Lastly, the juveniles are in development and mostly in the eagerness to be mature soon which takes away their happiness. While adult people are happy with the freedom to choose or let go due to their earning sources which helps them to take care of their needs and responsibilities.