Thank you for reaching out! Congratulations on getting into all these schools!

Being equally prestigious engineering schools, I would recommend UWaterloo (with UBC as second choice) just out of the co-op opportunities. Even if grad school is your main goal, having good co-op / internship experience will provide a leg up over other candidates and give you more options after graduating. I'll stay away from U of T out of its reputation for difficult grading, which will impact your grad school chances.

Also, don't discount the value of having a Canadian PR, since the American Green Card is much more difficult to obtain. Having that Canadian PR will certainly open more doors for you.

Cheers and good luck!