To get a better picture, let’s compare the two Institutes based on some common parameters:

• Faculties - Development Studies department at TISS and IIT Madras have highly esteemed professors imparting the best knowledge.
• Infrastructure: Infrastructure-wise, both institutes are fair and equal 
• Placements: The placement of DS is better at TISS than at IIT Madras. Students are offered placements and internship opportunities in very renowned NGOs like Pratham, Sneha, Aanandi, etc. The package offered is normal, and the maximum salary package offered is 22 LPA.
• Curriculum: This course is one of the best offered in the school of social work at TISS. Being one of the flagship courses of TISS, it's superior in quality to that offered at IIT Madras. 
• Brand name - IIT Madras is an engineering college while TISS is known for its social sciences specialization. Hence, it enjoys a better name globally and has a better research culture too.
• the quality of its research and researchers.
• Campus life: The ambiance at TISS is conducive to the requirements of the DS course and comprises several departments promoting social activities like social work, development studies, tribal studies, disability studies, etc. This aspect is missing at IIT Madras and the learning experience of this course is not on par with TISS.

For Development Studies only, I would strongly suggest you go for TISS.