Which one should I opt for: for IIIT Hyderabad CSD (Dual degree) or NIT Calicut CSE?

IIIT Hyderabad CSD would be a better option between the two if you like to study Computer Science as per the standards of US Universities. Otherwise, you can go for NIT Calicut CSE.

• IIIT H has a good brand name in the industry and this will definitely help in your career. Even if you wish to pursue higher education, you can get into top colleges because of the tag of IIIT H. 
• The institute focuses more on research as part of their curriculum, therefore it will definitely help in the higher studies. 
• Exclusive companies visit the campus during placements such as Tower Research, Rubric Inc, Apple, etc. 
• Google also hires interns at IIIT Hyderabad based on your GPA.

However, you should make the decision on your personal preference.