If you are truly passionate about Physics, be it theoretical or practical, you should choose either IISER Pune or IISER Kolkata. IISER Kolkata is the best option for Physics, while IISER Pune is well-known for its overall academics and infrastructure. Here are the reasons why you should prefer IISER over IIT.
Based on the performance over the last few years, IISER Pune will be better than IISER Kolkata.