Vancouver for me. Beautiful city with all kinds excursions to natural wonders. Not to mention the great food and beer and other attractions. I did a Rocky Mountaineer train trip from Vancouver to Jasper and then on to Lake Louise and Banff. It was first class and awesome. Can't go wrong with the Canadian Rockies IMO.
Vancouver is beautiful, but a bit sterile and lacking cultural bite. Would rather live there than visit (again)
Montreal is more exciting, more bombastic - better club culture style nightlife. But it's cold as balls for half the year, and very, very french. Again, LOVE visiting, but wouldn't want to live there 24/7
Vancouver is beautiful. Clean, better weather, utterly amazing natural surroundings. Much, MUCH more of an asian-pacific influence as well. However, as I mentioned, it's sterile a bit. Because of well intended and fantastically environmental minded zoning, the buildings are in many ways barely distinguishable downtown and the surrounding areas. Ever see a really beautiful, well matched to nature glass building with a lot of greenery (green roofs, gardens, etc)? They are beautiful. But when EVERY building sorta looks the same, it becomes dull, even as it's green and beautiful.
Vancouver would be a great place to live, imo. But to have a fantastic few days? Montreal, by a mile. Unless it's winter.