After doing some research online, I would say that all the courses at ISI Kolkata are amazing if you know which field you have to choose. Everything depends on your choice of the field as every field is distinct from one another.

Now, I would mention that for M.Tech CS & QROR, these are already well-established Programs and need no introduction. 

QROR:

• It’s a course based on subjects in applied statistics and business analytics.
• If you want to be in Business Analytics, it’s better than CS & Crypto.

CS:

• It has theoretical CS as well as Artificial Intelligence and Machine Learning Courses.
• This will give you ample opportunity to do a Ph.D. as well as jobs in Data science positions.
• If you like coding and discrete mathematics etc then this is a zone to play in.

Crypto:

• ISI has India’s best Crypto people.
• And this is the first year of M.Tech Crypto so there is not much data available.
• But if you are not good in Abstract algebra Number theory then say not to this course.
• Research opportunities after M.Tech Crypto will definitely be better than that of QROR or CS.

I hope this helps you in clearing how all the three courses are distinct from each other. Each has its different criteria and comfort.