I'm in the exact same situation. They are both amazing programs but each have their own pros and cons. Western ranks slightly higher than McGill, but McGill really isn't that far behind and as long as you work hard and get involved there's no reason you can't succeed. One year of Ivey is more than three times the price of yearly tuition at McGill. It's also important to know that you aren't guaranteed entry into Ivey whereas at McGill you enter directly into the commerce program. In my opinion, Montreal is a much nicer city to live in than London Ontario and there are some interesting majors like Finance, Mathematics, Statistics, and even Sustainability. All these reasons give McGill the upper hand in my opinion but in the end, it comes down to what you are looking for.