Go for IIT Guwahati CS. It's one of the older IITs which is not to be missed. What is NSIT? I dunno about you, but I wouldn't join NSIT leaving an old IIT.

Hey Ankit,

In Both of Above mentioned Colleges. I'll recommend you To Go for NSIT rather then IIT Guwahati. But depends on your choice as well. NSIT plus point is it's location. As it's located in Delhi. You will get good amount for internship as well as job opportunities. Regarding placements it has a decent placements as well. In case of IIT Guwahati it has its own advantage. As it's has better infrastructure obviously as it's IIT. So you could compare which you prefer the most.

Best of luck