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If you go to Quebec, definitely split your time between Quebec City and Montreal. Montreal is much larger (3rd largest city in Canada) and is very cosmopolitan in nature, more things to see/do in terms of sites, events, bars/restaurants, entertainment, etc. Quebec City is a much smaller and more provincial type city. But you can't go wrong in choosing either city if you want to eat well, see the history of French Canada and enjoy Europe without the costs!
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Actually, Montreal is by far the 2nd largest city in Canada, not 3rd. Vancouver is the 3rd biggest and not even half of the population of Montreal.
Glad you choose Quebec, Summer is fun here. Alberta is more the Rookies and the Great Nature like Banff and Jasper whereas the cities themselves could be kind of 'boring' because they are more business oriented than for tourists.