You should talk to archinect editor Mason White. He is the quintessential example of how to make the transition right!...my wife made the change the other way around though.
My opinion:
I love Toronto but compared to NYC is a little bit slower pace. Nevertheless everyone I meet in that city loves living there.

WWJJD?

Please, I really need info from insiders. I am partially familiar with arch scène in Toronto, it looks more interesting that the one in New York. Of course, I am desperately in love in this city and it will be the hardest to leave. If there is any Archinectner who made that switch this way or another, please share your experience. Thanks.

Let me preface by saying I've never been to Toronto so maybe you don't want my advice, but I do live in New York. Your question seems kind of silly to me. There's no other city like New York anywhere, there is no comparison. I would have to say that your living experience will probably be 100% different in any other city outside of New York.

Moving to a new city is a huge commitment, and everyone does it for their own different reasons, are you really going to base your decision on what people tell you on archinect?

I would still email Mason White. His experience has been great. He currently teaches at the University of Toronto, moved his practice there with his partner, and they have the coolest kid in that town for sure.
Anyways, he has also taught at the AA in London so the guy should have a pretty good sense and have very practical opinions on the matter.

toronto may be smaller, but it's better hung.

Are you Canadian?

I would think your key interest area is more accepted in Vancouver. Although, with family located in Alberta, I know first hand the inflation in that province from the oil wealth. They need both affordable housing and more emphasis on sustainable design.

I think the more bold move would be going to the frontiers that aren't necessarily strong on your interests. A place where you can sell your passion and make a much bigger splash.

Toronto is a great city, I'm not sure if it is the "green" place to be... It is a diverse metropolis, multicultural, might not have the same vibrant density that you are used to coming from new york... It's more spread out, you generally need a car, but the public transit is pretty good... It's maybe a bit closer to Chicago than New York I think... Some cool architecture, good night clubs, great food, multicultural, a great urban university campus with lectures, etc...

It's the third largest theatre city outside of New York and London...

I think how well you like Toronto will also depend on where you live... Do you plan to live and work downtown? Or would you be living more uptown or in the suburbs and commute in? It's probably the most "american" of the canadian cities (although its more culturally diverse than any american city)... There are big shopping malls, all of the big american city comforts but its genrally i think alot more international in its feel... It's probably not as exciting as new york although I've only ever been a tourist in new york...

I'd probably go there as a tourist first, look at the architecture, wander around and discover stuff... but know somebody in the city who can show you around...