Pros
Carries out extremely important, life saving work. An incredible mission and super rewarding. Lots of opportunities to really be in the thick of it, great career development, amazing coworkers that have dedicated their lives to this work, and a lot of prestige that comes with the role.
Cons
UNHCR will work you to death if you let them. Everyone that works there is an absolute workaholic and expects the same from you. There is absolutely no work-life balance. Any talk about self-care is complete lip-service. They also claim to be a human rights organization that cares about labor rights, but most of their contracts are for UN "volunteers" or UNOPS. They abuse this system to not pay their staff what they are entitled to and to avoid giving them benefits. Staff will put up with this for years (and even decades) because they love the mission and because of the prestige of working for the UN. This leads to an incredibly competitive work environment and it can be quite cut throat.