We (four retired adults) will be spending two weeks in these two cities this September 2022. We do not need to spend an equal amount of time in each, so are flexible in that sense. But we will be flying into Montreal from Seattle and returning to Seattle from QC and that's fixed.
We don't know much about either city except for some basics. We've always wanted to explore this part of Canada. We will not have a car, unless we decide to rent one for a day here and there in order to go out and about. We will travel from Montreal to QC via train.
What we need help on is deciding areas of each city to search for accommodations. Typically, we like self-catering accommodations, but are open to modest-priced hotels. We don't need/want to be situated in "party central" but do like easy access to the central city, either by foot or transit.
While we appreciate and enjoy what the core of any city has to offer, we also like settling into an in-city neighborhood with local shops and restaurants.
Hope this gives you enough to go on, and I appreciate any advice you can offer.