ISI is an Institution that is controlled by a single governing body but has different centers, unlike IITs which are governed by independent bodies.
This means, no matter if you study from any branch of ISI like Bangalore, Delhi, or Chennai, you will be awarded a degree from ISI Kolkata only because that’s the headquarters.
Therefore it makes no difference between the curriculum and value of both ISI Kolkata and Bangalore. The only difference between the institutes lies in the course that they offer. ISI Bangalore offers Bachelor’s course in Mathematics whereas, ISI Kolkata offers Bachelor's course in Statistics.
So, the choice of institute totally depends on whether you are interested in statistics or mathematics.