The main thing that all comes down to is what you want to do ahead in life.
Confused by this only decision, my friend inspite of having a decent rank in advance took Computer Science in BITS PILANI Goa(BITSAT score 364). When asked about the reason he told that he wasnt sure which subfield to choose but surely computer science can help him get into nearly any field in the future in the era of digitalization.
He was getting CSE in the new IITs too but he preferred quality over the IIT tag. Others might not have done the same in his position but he is confident that his decision was the right one.