As I have an experience of both IIT as well as NIT B.Tech. It seems I am eligible to answer the question.
After clearing jee main in my first attempt but wasn’t qualified to jee advance. So, I opted for NIT Bhopal because I don’t to be a dropper. After taking admission, day 1 ragged very badly in the night but luckily didn’t get slapped because I knew how to give introduction( Now the situation has improved a lot). Now, the quality of teaching in NIT and IIT have no comparison but for a few faculty, an exception is always there. The class will be taken by M.Tech faculty, although they have Ph.D. faculty too. There is always a mass bunk. All these stuff motivated me for IIT.
So, I started again preparing from January onwards cleared the jee main and qualified the jee advance too.