Oh wow i've been trying to decide between ubc and mcgill too! and i just accepted mcgill, because, well, i live in canada so for me, there's no doubt that mcgill is considered more prestigious and high quality. but for commerce, i think ontario universities would be a better choice than mcgill...i'm going for the arts and science programme. and french...french wouldn't necessarily be a problem there cuz basically everyone speaks english and french, and theres tons and tons of non-quebecois/francais students there so don't worry about that. Montreal is an amazing city to live in and meet other university students, cuz its really a huge island of universities. vancouver, on the other hand, is a beautiful harbour city with a great weather, except theres a lot of rain (which many people, like myself, enjoy). mind you, you'll find that vancouver has a big asian population, and hence the name "hong-couver". i personally like that about vancouver cuz i'm asian, but others avoid it precisely because of that.
well, i hope you make a satisfactory decision!