Both ISI Kolkata and ISI Delhi are excellent institutes offering the MS in Quantitative Economics program. It’s difficult to compare the two as they have similar admission criteria, placement, and even scholarship opportunities.
However, if I had been in your place, I would have chosen ISI Kolkata as it has more courses, professors, and students. The students get to interact with students in non-MSQE courses.
For M.S. in Quantitative Economics, ISI Kolkata is better than ISI Delhi. It offers better career prospects. You will have better job opportunities. Leading banks and consultancies take part in ISI Kolkata placements. The average CTC offered is around INR 17-18 LPA. Goldman Sachs, American Express, United Bank of Switzerland, etc. are some of the major recruiters that take part in the placement drive.
ISI Kolkata also has more courses. So, the student crowd on campus is diverse.
While both ISI Kolkata and ISI Delhi are at par, both have their own perks. If you are interested in job opportunities after completion of your course, ISI Kolkata is the better option. On the contrary, if you are interested in pursuing research(Ph.D.) after doing M.S, then ISI Delhi is a better option.
In the end, it totally depends on your interest whether you want to grab a job opportunity or want to pursue higher studies.