Toronto is the center of the business world in Canada, and most major companies are based there. It's a sprawling metropolis, reminds me of silicon valley: Between Hamilton and Oshawa it feels like a single continous city. Toroto has lots of ethnic flavour, and strong communities, and its share of big city problems. It's close to the US border -- crossing US borders at the airport is a breeze since all US border guards are well versed in the business travel routine. In fact, most likely most business dealings from Toronto to anywhere in US is probably better/easier than anywhere else in Canada.
Vancouver is on the west coast, and influenced by the mindset frequently found in US west-coast states and cities (Seattle and SF in particular). Its own mindset is somewhere between SF and Toronto.
Ottawa has strong software community, but it's not nearly as big as the above cities (it's located 2 hrs driving from Montreal, and 4 hrs from Toronto). It's got a heavy load of federal government agencies and money.
Montreal is more affordable than Toronto or Vancouver. In my opinion, it's one of the best places to live in Canada, though being located in a francophone province with a strong independent (some say chauvinist) streak, may add extra hassle for you as a business owner (due to legal language requirements, etc). Anglophones in Montreal have a love/hate relationship with the city/province -- all rooted in history and politics. But, guaranteed, if you embrace the experience living in this de-facto bilingual city, you won't regret living there.
Toronto and Vancouver are definitely more business oriented than Montreal for sure, in that order - Toronto > Vancouver > Montreal.
Vancouver is pretty nice, there's quite a bit to do. If you don't like wet weather than you may want to avoid Vancouver. Rains quite a bit here (think Seattle). One thing Vancouver has that (I think) is better than Montreal or Toronto is that it never gets extremely hot or extremely cold here. In the summer you're lucky if it hits 30C and in the winter we usually hover around -5C to 10C - unless you get a cold snap like we had a few weeks ago when it was around -15C.
Avoid anywhere between Vancouver and Toronto. The prairies suck - avoid at all costs.
Not sure about immigration but from the amount of immigrants in Canada I assume it can't be that hard. Starting a business is extremely simple - I helped a friend go through all the steps and it literally took a day to get the paperwork sorted (not even) and submit it for a sole proprietorship.
I'd lean towards Toronto a bit if you're looking for other startups and entrepreneurs. They're here in Vancouver, but nowhere near as many as the east coast.
(side note: if any vancouver HN peeps are having a meetup or want to plan one, let me know)
It's been a few years since I've spoken French on a daily basis, and I've always talked slang (from a francophone part of New Brunswick), but shouldn't you leave off the 'le'?
