McGill is not known for its MBA but it's McGill at the end of the day. If branding is important for MBA then McGill has some weight in Canada. Further, I don't think there is anything to learn in school, you probably have learned more as a professional than you ever would in your MBA, it's more like networking and forming ties.
Don't know about UBC but they should be comparable to all other Canadian MBAs. After all, how big is canada how many good schools are there in Canada.........Rotman, Schulich, Queen's, Ivey, Sauders, Desautels, HEC.........I think you'll be fine if you get into any of these.
So it boils down to where you wanna live for a year or so. Vancouver has a nice weather and English-speaking. Montreal is cold, can be very trashy and speaks French most times.