Vantaggi
There's a certain amount of cachet in working at the World Bank, particularly in DC, where people actually know what it is. Presumably if you're in the right department, there's fulfilling and relevant work to be done. Excellent pension program. Good salaries, provided you're not an American and subject to additional taxes while your foreign colleagues pay none.
Svantaggi
Absolutely zero career mobility. I would say most job postings are ultimately fake and intended for a candidate already in the department, but since promotions generally aren't allowed, everyone's time is wasted with phony recruitment drives. Under-performing staff has so many institutional ways to make life hard for their managers that most managers don't even bother to try to make them work. If you're an American, the tax situation is a nightmare. HR staff is useless. Constant reorganization of departments with minimal communication.