You're better off staying in Downtown Toronto. Assuming you're talking about YYZ, it's outside of the city limit and isn't connected to the subway. There's an express train that runs from YYZ to downtown Toronto but it's almost $30 each way. You can take a combination of a bus and subway to downtown Toronto from the airport, but it is not worth the frustration!

Uber in Toronto is fine, however expect surge pricing during rush hour and after midnight in the downtown area.