Which is better: St. Petersburg State University or St. Petersburg Polytechnic University?

Question

Physics

I'm already on the threshold of admission, but I can't choose everything.
Interested in the topic of biomechanics, there are two developments: go to St. Petersburg State University to study mathematics (but the fundamental level, without deepening into the biosphere); go to the Polytechnic for mathmechanics (but with a possible profile in biomechanics)

The problem is that I cannot be sure about the Polytechnic because of the many negative reviews about him, that he "rolled down".
While SPbU is still in high positions in the ranking, but, as far as I understand, it involves a very difficult educational process (on MatMech

) topic

What can you say about this?