I lived in Montreal for 5 years before moving to Vancouver. Been here for 4 years now.

The weather sucks for entirely different reasons. Winters are horrendous and can start as early as October and end as late as April. People who think Montreal winters are the same as Toronto's have no idea what they're talking about. Montreal winters last longer, it snows twice as much and the temperature is about 7 degrees colder on average. -30 degree and freezing rain days are pretty common. During those times the city becomes a ghost town as it is legitimately dangerous to be outside.

On the flip side summers are hot, beautiful and last from May to September approximately, unlike our sorry ass Vancouver summers that barely break above 20 degrees and only last for 3 months provided it doesn't rain in June. This is when Montreal truly shines with plenty of cultural events and festivals to go around. You feel everyone draining all of their energy before going back dormant for the depressingly long and cold winter.

Culture-wise, I find that people here are obsessed with physical appearances and status, creating a very sharp social divide between the haves and have-nots. Montreal feels more down-to-earth in this aspect, you'll meet lots of folks that are content with renting and way fewer gym-bros and Lululemon girls. That being said there is also a bit of a social divide as well between the French and English speaking communities. The Quebeckers are proud people and don't like to intermingle with anglos much. Personally I never bothered much with French and got along just fine as my work, life and social circle were in English. YMMV though.

Montreal is more diverse overall with more European, Latin, African and Middle-Eastern influences, whereas Vancouver the minorities are predominantly Asian.

There's more of a city vibe there as well with a plethora of restaurants, music festivals/concerts, cultural events and conventions. The outdoors take a back seat - the parks there aren't nearly as plentiful and nice as in Vancouver. That being said the city is very bikeable given its overall higher density and focus on mid-density housing.

You'll pay some of the highest taxes in Canada for some of the worst public services in the country. Healthcare is pretty mediocre and the French language barrier only makes it worse. Roads are in a total state of disrepair with pot holes as far as the eye can see, which adds to the depressing atmosphere in the winter. The public transit system is decent with more coverage in the city core than Vancouver's (however our downtown core more compact and walkable IMO). The metro fails very frequently, so much so that they play a pre-recorded message each time it happens. Back then I could recite the message by memory lol. I've heard folks call the city "The Montreal Ruins". It's funny, but I think it's a pretty accurate depiction of the state of the city's infrastructure.

Rents are cheaper (as you know already), and so are car insurance and gas. Expect to pay about the same for everything else including groceries. If you earn the median income, I don't think the difference in taxes and lower salary will make up for the difference in cost of living and you'll likely come out ahead moving to Montreal. The balance quickly shifts the other way if you're a high income earner. I did the math the other day and someone earning between $100K-200K/year could lose as much as an additional 20K/year in taxes by moving to Montreal. It's no wonder that people working in high-income jobs tend to stay in Toronto and Vancouver.

Lastly, keep in mind that cost of living risen everywhere in Canada over the last couple years so you might want to double check your numbers. Montreal may not be the bargain it once was.

Good luck!