I've been to both, and while I am biased this is the easiest decision I have probably ever had to make.
I've been to Toronto, and it was alright. I then went out of the city for a day and it was awful.
The USA has many different kinds of cities. There is a lot of variety. There are cities that are extremely hot all year like Miami. There are cities like Boston and Chicago where it gets extremely cold. We have mountain ranges. We have two oceans (well, Canada has mountain ranges and two oceans as well, but the water in the Atlantic and Pacific is too cold to swim in up north). The USA has Hollywood. The only reason any movies/television shows are shot in Canada is because it is cheap.
The cities in the USA are cooler and more exciting than those in Canada. We have Los Angeles, Miami, Seattle, New York, New Orleans, Boston, Philly, Washinton, Las Vegas, Honolulu, San Juan, etc. Canada has what? Toronto, Vancouver, and Montreal?
I honestly don't give a **** about "Quality of life" ratings. The USA is naturally more diverse than Canada. In the USA, it can be -30 degrees in one place, and 80 degrees in another on the same day! The USA has Caribbean Islands, the Grand Canyon, Hawaii, etc. Canada only has a bunch of mountains and Niagra Falls, and the USA has both too!
Their cities may be cleaner, but there is more to a city than that. I think New York is dirty and that needs to be changed, but there is so much more to do in a city like Los Angeles and Las Vegas than there is to do in Vancouver or Toronto.
They call Canada "America Junior" for a reason. I have nothing against Canada, but I do think there is more to do in the USA.