As someone who lived in Montreal for 4 years, it gets old pretty quick. I now live in Brooklyn for comparable prices to what I paid in Montreal (rent is a bit more, but food is dirt cheap in NY) and like it much more.
1) Verizon has twice as many subscribers as Canada's population. The US is a way bigger market.
2) Generally people aren't as excited about your ideas as they are in SF or NYC. People here seem to be way more receptive to innovation.
That being said, Canada has a great education system and there are a lot of smart motherfuckers. Too bad the immigration situation kind of sucks for founders.
Disclosure: I am Canadian