While all three institutes are prestigious institutes, my sister chose ISI Kolkata for a number of reasons. Here are a few reasons

• ISI Kolkata is the best institute when it comes to Maths and it is ranked #1401+ in QS World University Rankings 2024. Its flagship course is B.Stat. 
• In this modern era, Statistics is highly demanded and ISI opens opportunities in the same. 
• The placement scenario of ISI Kolkata is at par with the top IITS. The average package recorded is INR 25.50 LPA while the highest stood at INR 89 LPA.  
• The institute offers a full scholarship and currently, a number of ISI pass-outs are undergoing PhD programs in top foreign universities.
• ISI has no tuition fees except hostel fees. In fact, students get an annual scholarship of Rs. 36,000/-.
• The small batch size improved the student-teacher ratio as a result all students got individual attention.
• The accommodation facilities are great and students are allotted single occupancy rooms. 

ISI Kolkata is a great option as it offers opportunities in both, jobs and higher education.

ISI Kolkata is the best option for MSc in Maths, followed by IISc. IIT KGP is reputed in the technology domain, but for core science subjects, it’s not a good option. If you are interested to pursue pure Mathematics, choosing ISI is the best option among these. It specializes in the field. You will get better career opportunities and exposure in the field.