IIT Madras is the best choice for MTech in Chemical Engineering. Some reasons that support my claim are

• Being a metropolitan, Madras ensures better living standards and transport facilities thus attracting more faculty.
• The R and D centers of most top MNCs are located in Bangalore and Mumbai. Owing to the proximity Madras is preferred over KGP.
• Most process industries prefer BTech students over MTech students as chemical engineers. Only R and D and Consulting companies look for MTech students for core jobs.
• Better facilities attract better students thus you will find a better class of peers at IIT Madras in contrast to IIT KGP.
• The faculty comprises professors belonging to various fields and cultures whereas IIT KGP has more Bengali professors.

Thus, considering the demand for PG students and facilities at IIT Madras, it seems to be a better option for MTech than KGP.