My brother has visited both institutes. So, I know a little bit about NIT Calicut and IIIT Bangalore. If you're talking about B. Tech in CSE, NITC is undoubtedly the best.
NITC remains ahead in terms of ranking compared to IIITB. But this doesn't necessarily mean that IIITB is not a good college. IIITB is a pretty new college and has only been offering M. Tech in IT for a long time, and this is one of the reasons why it does not have much recognition among students.
IIITB does not have a B. Tech program, but recently it started offering a 5-year Integrated M. Tech program. Right now, the second batch is about to pass. The first batch has passed out with remarkable achievements. IIITB has been more of an M. Tech-focused institute since its start. The faculties are really good here.
Placements: When it comes to placement IIITB gets the upper hand. Being situated in Bangalore, the college also attracts a lot of software companies.
Infrastructure: In terms of infrastructure, NIT Calicut is way better than IIIT Bangalore.
Academics:
So, go through the above-mentioned points and make your decision wisely.