Do you think IIIT Delhi should be preferred over the top 3 NITs (Trichy, Warangal and surathkal) by a South Indian when there is passion for coding?

Yes, you can go for IIIT Delhi without any second thought. The institute has come a long way and it has improved its reputation. It can easily compete with some of the most sought-after institutes. 

• Placements: In its latest placement season, more than 140 companies have visited the campus and made a total of 585 offers to its students. The highest domestic package was INR 50 LPA and the international offer was INR 37.50 LPA. The average package offered was INR 16.14 LPA.
• Faculty: It can obviously be said with certainty that the faculty of IIIT Delhi is enviable and can stand toe to toe with the institutes mentioned in the question.
• Coding Culture: IIITD has dedicated clubs with great coding culture for students. Previously, 15 students got selected for Google Summer of Code.
• Hostels: The hostel rooms at this institute are much better than any government college. Proper air-conditioning is provided at nights during summers and heaters during winters.
• Location: IIITD enjoys the locational advantage of being situated in the capital city. You will be given great exposure and opportunities. NITs, on the other hand, are located far away from the cities and you may face travel problems.

Some of the disadvantages that you may encounter at IIITD are the reputation and campus life that NITs carries. They are more reputable than IIITD and have a great campus life.