Hi, if you are not sure of metallurgy and material science that this is what you want to do for the rest of your life than it is advised to not take up a branch that is very specialized. You can opt for more open branches like Mechanical, CS, IT. Chemical Engineering has a huge demand when it comes for Job opportunities. It would be a safer option than to go for Metallurgy and material Science. If you think that the new IIT you got Mechanical in is going to bloom over the years than it is fine. If you think that the value of that IIT won't be that much you can ignore. If you are ready to compromise with the IITs you wish to get in then you can choose Chemical or Mechanical. Below is the link for you to compare your colleges and it will help you narrow down your choices.

https://www.careers360.com/compare-colleges

Hope this helps. If you still have doubts please feel free to comment.