I still don’t understand why people have to choose between colleges. Rather than the institute, what matters is what you learn from the college. Many people from IITs regret not choosing a different field while many are content with their decision. It all comes down to what you like and want to pursue. Coming back to your question, I am going to answer it very objectively. IIT Madras is a good choice from the learning perspective whereas IIM is a good choice from ROI perspective. You are smart enough to gauge the situation. If it’s the money you are after IIM is for you but if it’s the knowledge you are seeking, IIT it is.