I think this question has come up many times. It depends on what you want. If you are looking for a very French, very scenic, very old city; choose Quebec City. If you are looking for a very cosmpolitan city with lots of nightlife, great restaurants and shopping; choose Montreal. Of course this is a very general guideline, both cities have some of each. Montreal is much bigger, slightly less expensive, not nearly as scenic.

I think Zootsi's guidelines give you a feel for which city you might wish to choose. Also, Montreal is considerably more ethnically diverse, with a more international feel. The Italian, Hispanic, Arabic, Portuguese, Greek, Jewish, Chinese, Filipino, English communities are quite large, to name a few. Quebec is 95% French-speaking, by and large descendants of New France, Quebecois de souche as they say.

I would add to this advice that I think BOTH are great long-weekend destinations. If the cities still seem a toss-up to you, one reason that could tip the balance to potentially Montreal would be time consideration; if, for example, you are coming from Washington, Chicago, Dallas, to name a few cities, there are direct flights to Montreal but not Quebec. That would give you more time to explore and less time in transit, which would allow you to maximize your time if you only have say a 3-day weekend.

You won't go wrong whichever you decide.

DAN