Pros
As a consultant, and I only speak for consultant positions, you can use the experience to learn and grow professionally, as a bouncing board to other international organizations. As a consultant never spend more than 3 years at The World bank because it is not worth it due to the lack of benefits unless your hourly rate is very high (400 daily), and you have benefits coming in through a family member. It is best to work at another international organization as a staff full time employee. Please note: this is just advice for people as consultants. Full-time employees have excellent benefits, reviews, and upward mobility opportunities.
Cons
As a consultant you are not a staff member and so are treated with a different set of benefits. Be smart in learning as much from the opportunity and then supplementing your work with either work in another organization, more studies, unless you are a retiree.