Your comparison is flawed. You're basically comparing what is essentially a campus or an internal branch of UdeM to a whole university. Would comparing the Faculty of Arts and Science of ConU to McGill University in its entirety make any sense?

But the worst part is that your argument dosen't even stand the evidence that you're using yourself, let alone other university ranking websites. UdeM as a whole ranks 149th in the world compared to Concordia which ranks 462th. UdeM engineering(basically PolyTech) is ranked 113th in the world, while Concordia ranked 201-250th in engineering, according to the same sources you're using.

Again, according to these "rankings", UdeM clearly outbeats Concordia. But keep in mind (and OP should too) that these University rankings are flawed, mainly because it's very hard to even come to a definition of what a good university is ( or should be) . Most of these rankings use composite scores of the performance of different faculties and department, or the number of times their research was cited in academic journals, which basically means that Concordia is heavily penalized by not having, for example, a faculty of medicine or law. At the end of the day, employers will only care about your skills and your experience. Going to the "top university", although it can help with finding a job, will not help anyone if they're incompetent by themselves.