What you can do to get better information than random anecdotes is:
A. Find someone familiar with math and economics (or one for each subject), such as those who graduated with these majors (for economics, should be someone who took a more math-based path).
B. Find the course web pages of common and representative upper level courses at each college. Examples would be real analysis and abstract algebra for math, intermediate micro and macro economics and econometrics for economics.
C. Note textbooks used and how much of them the courses go through, and have the people you found for A review the course notes, assignments, and exams. They can help you determine whether there are significant differences in difficulty or workload (which are not necessarily the same thing) between each school for the courses in question.
Obviously, this is limited if you cannot find people for A, or if the colleges in question do not make course web pages publicly visible.
Here is an older discussion with a similar theme, where @bernie12 had done this type of inspection of specific courses, though mainly in chemistry and biology, rather than math and economics: