If you like old architecture, sight-seeing, and such, you should probably go to Quebec City. It would be better still in February, when the winter carnival starts, but you can still see a lot of things and have that old European charm to the whole city. There is much more French prevalence in Quebec City, but most services (hotels, restaurants) are available in both French and English as they cater to tourists.
In Montreal, you will have much more of a nightlife, as well as the sightseeing, cobblestones in the Old Port, walks on Mount Royal, etc. Montreal's downtown core becomes a bustling nightlife crowd after 8PM on weekends and THU-FRI nights, so you could dance, go to a comedy club, or if you want to spice up the honeymoon, both of you can attend a "gentlmen's club" and then re-enact some of the dances later that evening in the hotel room {wink!}
Winter in Montreal and Quebec City can be quite snowy, cold, and windy. In December this year, we have already had two large snowfalls (12" or more each time) although this is uncharacteristic this early in the year.
One advantage Montreal has to Quebec City is that we have a subway and series of underground malls that you can shop and travel around town without having to step outside for too long periods.
If you are from Alberta or B.C., you don't need to be impressed with ski hills or such out here in Quebec, so my suggestion would be:
1) Do you want to relax, enjoy old world charm, and have a laid back romantic honeymoon? Go with Quebec City.
2) If you want to party hard, be in a more cosmopolitain city, and have much more things to do and see around town, go with Montreal.
Oh and keep in mind that Quebec City is only three hours away from Montreal, so you could take a day, drive to the other city, and see a few things that you might have wanted to see, then drive back. Another alternative is the VIA Rail train that runs daily between Quebec City and Montreal.