IIM Ranchi or IIM Trichy
As far as I am aware, IIM Ranchi has the best placements among the new IIMs. But since I am a student of neither, I would strongly recommend you to talk to the current students and alums. Do not restrict your parameters to placements and academics alone. Try to know more about the campus life and other small things that most overlook at this stage. Pen down all that you gather and decide on the basis of your priorities. I know this can be a cumbersome exercise and you might be back to square one over and over again but I strongly believe, you would find your answer somewhere in the process. Good luck!