Each substance has its own profile of consequences and harms. In some way, the question is really comparing apples to oranges.
Cannabis use very clearly cause problems with mental health disorders and problems in functioning. By the way, those are harder to pick up because, typically, monitoring systems are picking up things such as heart disease and lung cancer, the classic problems with smoking. They are not so good at picking up depression or underemployment, so we can miss some of those. That's an important point.
To ask which of those is more harmful is really not such a logical question. I think both of those outcomes are bad. We'd like to avoid all of them. To me, trying to compare the substances doesn't make a whole lot of sense.