^^^ Very helpful. Congrats, you have some wonderful choices! You can get a top-notch education at all of them.
I know these US schools well, Toronto not so much.
Purdue–This is one of the premier state (public) STEM universities. It is a large state school with big-time sports. Home football games will be a big deal on fall weekends. Basketball is big too. Of course, you can ignore all of that if it hold no interest for you. It is in a college town, so a lot of the local economy is geared around the school, the students, and the faculty. Many of the students will be in science, engineering, math, etc., so will be on same page with you.
Case Western, or CWRU (pronounced Crew)–It is a medium-size national university. It’s in a very nice part of Cleveland, which often gets put down in the US, but is, in reality, a pretty nice city. CWRU used to be two schools (Case Institute of Technology and Western Reserve College), so the campus is really two merged campuses, with Euclid Avenue splitting them. Euclid has had a lot of redevelopment in recent years, and there are many restaurants, bars, coffee places, etc. geared toward students. Little Italy is just a few blocks off campus and also has some good restaurants accessible to students. There are a lot of cultural institutions right around campus–art museum, symphony hall, history museum, etc. Most freshmen live in a cluster of dorms on one side of campus, and then on the other side of campus sophomore year. Greek life seems pretty mild to me compared to other places–that is, not too crazy.
WPI–This is also a medium-size national university. We loved the campus–it was really one of our very favorite out of very many. It’s in a nice area of Worcester (pronounced Wus-ster or Wus-ta by locals), and Worcester has been improving greatly in recent years. As noted above, it is unique in its hands-on, project-oriented approach. A large % of academic credit is earned working on projects. So that would be a big question for YOU–is that preferable, or would you prefer more of a traditional classroom approach to learning, although computer science is pretty project-oriented anyway. Also, students take 3 classes at a time, rather than the 4 or 5 that is standard at almost every other college/university. The classes move faster but you have less to juggle.
I’ll also note that WPI has been working toward achieving great gender balance in the last couple of years. The vast majority of US college students are females. However, STEM schools like all of these typically have a larger % of male students. WPI has really closed the gap. You could check, but I think CWRU and Purdue might have larger % of male students.
Good luck!