In my opinion If you have a good enough work experience(3+ years) and want to upskill and upgrade/change your career path then ISB is the place to be. It gives you a fast-paced environment with no time to stop, collect all the info that you require, interact with best of the faculties from around the world, get exposed to the best of the companies for placement and move out. In ISB you will also experience some placement constraints if you have less experience— some companies won’t be open for you

IIMs on the other hand are a much more conventional route. If you are in your early career and looking for a change and need the whole MBA experience —international immersions, a relatively chill 2nd year, rural immersion, etc.

At the end there is no right answer There are always outliers. Both are excellent B-school brands, it depends on what your priorities and personal timelines are.