Well, I would if you are worried about job prospects and all stuff although being in ISI Kolkata then shed off your worry. Trust me; you will get a job with an average CTC matching with top B-Schools in India. Job roles such as Business Analyst/Data Scientist and many others will be offered to you.

Now let me help you more in understanding this. Let’s break this into two parts – Job vs. Higher Studies.

• Pursuing Ph.D./Higher Studies is a tough deal if you're applying abroad.
• My personal perspective, in this case, will be, go for a Ph.D. in Industrial Engineering domain. 
• That's the best option, as it will be aligned with QROR.
• Now, you should definitely rethink before applying for the courses like Data Science/ Machine Learning domain, or Statistics.
• For this, I would suggest you consider doing some projects. And if you are at the Indian Statistical Institute you will get a plethora of opportunities.

So first and foremost, just be crystal clear with your future endeavors before joining any course. Once you decide, opt for the best but don’t rush. Just give your best thought and calculate all the pros and cons.