I have a few friends at both XLRI and IIM A and based on the interaction I had with them, I will say that rigor is similar to a greater extent. It is more of a choice - you can choose to let loose or work hard. You can choose to study 3, 4, or 5 hours additionally to have a strong foundation over a topic or simply not.
Academic Rigor - Ranking (XLRI>IIM A):
If we judge these institutes based on the data collected by the Govt. of India, then XLRI coursework is more rigorous as compared to IIM A.
In ranking, Graduation Outcome (GO) is the determining factor of teaching and learning ability of the students, graduation average, success of securing good placements, going for higher education. It is measured based on various parameters such as placement average, Median CTC, percentage of students going for higher education, etc.
There’s a sub-parameter called GPH, i.e. combined matric for placements and higher studies under GO. It shows the academic rigor of an institute. According to the recent statistics, the scores are as follows.
However, rigor is dependent on an individual's decisions and perspectives hence it tends to vary significantly from student to student.