Vantaggi
Two reasons - the mission of the organization (a world free of poverty) and if you are in "operations" you will have countless opportunities to travel across the globe - but it often comes with a steep price of (i) heavy and demanding work loads and (ii) poor work/life balance.
Svantaggi
large and stiffling bureaucracy; long hours - travelling and being away from home for weeks at a time; poor performance management systems - although staff complaints have been constant for years, management has not taken any serious action; HR management is very weak; compensation used to be the best around - but no loger as opportunities in the private sector (not just in the US) are much more competitive and the Bank is losing its ability to recruit and retain the best talent.