Both teachers are marvelous no doubt but from my experience and my friends MC sir is for those student who is more than average.That type of student can catch his each n every point bcuz his calculation is very fast normal student can't catch his method of calculation.One thing more you have to keep his slides with u during lecture session for better understanding and to copup with him.
The advantage with MC sir what I felt that ur syllabus finishes very fast with better understanding.
Now come to GB sir he is the one who have capabilities to enhance the study of even poor student in maths with his funny tricks and method of teaching.
But the one disadvantage which I felt that ur syllabus will last very long.Otherwise every thing is good with him
Hope this will solve ur query😊