Firstly, congratulations brother for cracking JEE advanced with such a good rank.

Well, let me make this clear, that you will be in your college for 5 years in succession. So, be ready to take that challenge but you'll also get a chance to enjoy your campus life a year more :)

Rearding choices, 

Campus life - IIT KGP > IIT G

Infrastructure - IIT G (best infra among eng. colleges of our country) > IIT KGP (it is also one of the best)

Academic Pressure - IIT KGP > IIT G

Peer group quality - IIT KPG >> IIT G

So, I would recommend you to join IIT KGP

Thank You