I want to work for IMF/WB?

A certain Praveen Kishore comments on the Dani Rodrik's blog sometime back- which worries me a bit about the type of people who get attracted to jobs at multi-lateral institutions.

For past three months, I have been collecting information regarding Ph.D. in Eco. and MPA/ID and similar other programs. I have gone through other blogs as well. However,I am still not decided about Ph.D. or MPA/ID. I like economics. I have basic undergraduate degree in Eco.and Mathematics. Thereafter, I got MBA(Finance) from Calcutta University (India) and Masters in Public-policy and Management from IIMB (Indian Institute of Management, Bangalrore, India). I am part of permanent Indian civil service (IRS - Indian Revenue Service, to be precise) with around 10 years of experience in Central (Federal) direct tax department, Ministry of Finance, Govt. of India - at operational as well as policy level. I am aged 35 years.

I want to work for IMF/WB or consulting organization. I also like academics/research.

In such a situation -What should I do? MPA/ID or Ph.D.in Eco?