Hi aspirant, in today's time, in my opinion IIIT Delhi is a better institute than NIT Delhi , this is due to the consideration with regards of the placements and establishment of the institutes. Also, IIIT Delhi is older institute than NIT Delhi. It is much more established than the other and offers better placements too.

For more comparison you can take the below mentioned link;

https://www.careers360.com/compare-colleges

Thank you.