Rather than telling you what to choose, I will list down the pros and cons of both the B Schools and leave it to you to make the final decision.
Mannheim Business School, Germany
Pros
Cons
IIM Bangalore
Pros
Cons
Weighing both the pros and cons you can now make a decision easily. In my opinion, go for the German B School if you have plans for permanently settling abroad. But if you want to eventually stay in your home country then IIM Bangalore is the best option for you.