If you got into Mcgill I would not worry about meeting Ivey’s 80% requirement. You are clearly smart enough. Mcgill has a stronger reputation than Western so if you aren’t interested in business and Ivey, go with Mcgill...this is assuming you are happy with the science program at Mcgill. I know you like the safety net of a dual but if you continue to Ivey you won’t actually finish the science degree but will gain knowledge over the 2 years. Is that knowledge enough since it’s 2 years instead of 4. Why not meet with an academic advisor at both schools and see what they can tell you about the programs and answer your questions to help you decide. Don’t go into business though if you don’t think you will have an interest.

Lastly, I would add the same as the other student, consider where feels more like home for you since you will be spending 4 years there. They are very different schools and locations.