Is the academic rigour of IIM Calcutta more than IIM Bangalore?

Yes, the academic rigour of IIM Calcutta is more than IIM Bangalore. But to a very little extent. Overall the impact is very little.

The academic rigour at any institute is affected by:

• Batch-size

• Curriculum structure 

• Grading 

IIM Calcutta has the largest batch size. So the academic rigor is higher than other IIMs. Also, it has the fastest academic year. There are no breaks between terms, and midterms are wrapped, in most years, within 3 days with 2–3 exams per day. IIM Calcutta has a Grading scale upto 9 with grades very spaced out within the batch, and competition for superior grades often heats up towards the end of Term 3, with average performance spiking up as everyone wants to score high.

The rest is for you to judge. But keep in mind that the competition vigor at every IIM is the same.