ive lived my whole life in Toronto, but id still maybe lean towards montreal. only deterrent would probably be the harsh winter, but you might be thicker skinned than i. its definitely the cheapest of the 3 cities and the beer flows like wine, so maybe i dont even need to go on?
never been to vancouver, but a lot of my friends have gone for extended periods of time and the reactions seem to be completely split down the middle on whether they preferred toronto or vancouver. from what i gathered vancouver is amazing for everything nature, but you need a car to get the full experience(most people ive talked to said they had the best time taking short trips out of the city)
i'm not a wilderness guy, so i cant really give any opinion on camping or doing stuff outside of toronto. however i think the city is tons of fun to live in. great skating, lots of not so obvious untouched spots. im not much for parks, but theres a decent amount(i think vancouver has it beat by a lot in that department though). Party wise, i really like toronto, there never really seems to be a shortage of stuff to do
so that was more of a rant than anything, but it might help you out a little. also, since you mentioned new york, think about what other cities you'd want to visit. Toronto and Montreal are close to each, as well as new york, philly, washington dc, detroit and chicago. If youre more interested in checking out seattle, portland, sf and if you wanna make the mission, southern california. then go to vancouver