I will tell you some points, based on which you can decide for yourself.
- College life: in the IIIT Allahabad, you will find a pretty strict studious environment. you will mostly spend your time in doing assignments. Compared to this, you will find a bit chilled out environment in NITT. the number of clubs in IIITA is also much lesser than those in NITT. The Fest is better in NITT. NITT wins here
- Coding culture: In this field, IIITA will win as the coding culture there, is much better than NITT, as majority of students in IIITA are coders, while NITT will have a high percentage of students belonging to core branches also. IIITA wins here
- If you wish to pursue MS. in international Universities, IIITA will be better for you.
- Placements: I did not find a significant difference in the placement packages offered in both the institutes. both are at par here.