Duty or Friendship?

Which one is worse: betraying one's duty or betraying one's friendship? 
I think betraying one's friendship is worse than betraying one's duty. One's duty is more like a personally thing or issue. If one betray it, it is only him that need to face the consequences. If  one betray his friendship, not only him, but his friend will be depress and sad. He does not only create problems for himself but also his friends and people around him. It is easier to make up what you need to do, like try harder next time or make it up by doing something else. But once you betray your friend, it is very hard to be friends again. There is a quote "Friendship is delicate as a glass, once broken it can be fixed but there will always be cracks" which basically means that it is impossible to be the kind of friends before once one had betray the other.