Hello mridul 

The selection of department is completely dependent on your choice. This will be dependent on your interest of field. 

If you are compromised with any department then chemical engineering in nit is far more better than IT or CSE in IIIT's. Chemical engineering is one of the oldest departments in our country and even there are so many opportunities in this department and even for it and cse dept also. But the nit tag matters alot.

Make sure that the nit would be old nits or top 15 then it will be more beneficial to you.

All the best for your future.