What should I choose between CSD at IIIT Delhi and IT at DTU?

CSD and IT have practically the same core subjects. You’ll have a similar curriculum in either of the options. Unless you have a strong interest in the design aspect of CSD, the choice is mainly between the two colleges.

IIITD is very research-oriented. It has state-of-the-art research labs and facilities. You’ll be exposed to dedicated and active research groups over there. Academics are taken quite seriously. You’ll study your subjects in depth for the next 4-5 years. 

At DTU on the other hand, academics are very laid back. You’ll get lots of time for extracurriculars. You can polish your skills in the area of your interest. 

If you are sure to build a future in Computer Science, join IIIT Delhi. But if you wish to explore yourself, and polish your skills in some other field, join DTU.