PhD or IB and MBA?

I am currently an undecided undergrad student that is very interested in economics and business, however I feel that an MBA may not be rigorous enough for my liking (I've heard you basically just use powerpoint and excel with very little math or stats). I am thinking of pursuing a BS in Economics or possibly a dual-degree in Math & Econ/ Econ & International Relations  (possibly some CS as well). I have always been interested in doing economic research (especially macroeconomic research) at places like the IMF/World Bank which has drawn me to doing a PhD. The thing I am struggling with is just how hard it is to get into a top-10 PhD program compared to a MBA (for reference its probably close to 5x as hard to get a PhD at Harvard than go to HBS, given the necessary math classes and research). I am an above average math student, but it seems I need to be basically the top student in my class to get into one of these PhD programs. So, I have begun thinking about more quantitive roles at PE or HF and I am wondering what paths I should take to get to these jobs. PhDs usually can get these jobs and are usually able to skip the more entry level phases but I was wondering if there are more Calc 3/Linear Algebra based MBAs or if MFE/CFA would be better, or even if a PhD in Finance/Stats would be easier. The problem I come into there is job mobility as I would like to not be stuck in finance for my entire career. 

Any help is greatly appreciated.