Here's a good paper on the topic from the faculty perspective:
What, how and why is problem-based learning in medical education?
A Harvard med student's perspective
Problem-based learning in medical school: A student's perspective
Using critical thinking skills and applying basic science information to a case while finding and augmenting knowledge gaps and using writing and speaking to consolodate new information does help students learn when compared to passive activities such as listening to lectures and reading texts.
Now someone will chime in and say that it is a time sink and that they learn better sitting at home with Anki and a pot of coffee but the board scores don't lie.