MBA from IIM / ISB and CFA – these are two very different career paths and the selection between the two would depend on what you want to do post your MBA/CFA.
An MBA is a general management degree and while you do choose your specialisation in the second half of your course, the first half concentrates on giving you a general all round approach to the different subjects in management. A CFA on the other hand is highly specialised and meant only for finance professionals. In fact while in the subjects covered in CFA Level 1 & 2 are similar to the subjects in an MBA in Finance, Level 3 takes you much deeper into the subjects than most MBA courses. Hence, it depends on the career path you want to choose. Only if you want to get into hardcore finance like research, investment banking etc should you choose CFA.
Another point to consider is where do you want to live and work in the longer term. Industry dynamics in India are very different from dynamics abroad. In India, most people do a CFA in addition to an MBA given that most companies have a basic minimum requirement of an MBA degree. However, this is not be true for other countries. A professional certification like a CFA alone may be good enough for you to get a core finance job in a city like London.
Now with regards to selecting an institute to pursue your MBA like IIM & ISB, you may confuse yourself by looking at various rankings of top bschools in India etc. What finally matters to most people is the boils down to just two things while making the you would probably benefit more from the huge alumni base of the former & better industry reputation of the IIM brand.
This is a personal opinion of Rohit Chadda. He is an IIM Calcutta alumnus 2009 and famous for his entrepreneurial venture foodpanda.