What is the difference between the preparation strategy for GATE and that of M Tech (CS) at ISI Kolkata?

I am not fully aware of IITs courses but could still try to give some insight of the same on whatever I got to know from the internet. 

• The ISI M.Tech CS entrance exam includes an optional Objective Paper Mathematics and a Subjective Paper (you may choose CS).
• The majority of ISI's placements are in analytics firms so it would be advised to not choose ISI if you're looking for a core CS job.
• If you are interested in Algorithm Design, Machine Learning, and, most importantly, Cryptography, then ISI would be a good option. 
• After completing your MTech CS at ISI, you will have several research opportunities in ISI and also abroad.
• ISI has excellent theoretical CS faculty (Mathematics, Statistics, Cryptography, Machine Learning, Data Science). 
• So, if you're interested in learning more about these topics, you can come to ISI.

Please do not expect to find Developer, Coder, or Core CS work at ISI after completing your M.Tech. Students have a misconception about it and come here with high hopes which ultimately backfires.