I have mentioned this on other threads, but I feel zoos should specialize in animals that fit their climate. Last January I spent two days at the mountainside zoo in Colorado Springs photographing siberian tiger and grizzly bear in the snow, which was great. In fact, without the snow this zoo would be somewhat dull. I know Minnesota Zoo also specializes in cold climate animals and I think they even let people cross-country ski on the zoo's large grounds. As Meaghan mentioned, I'm sure Toronto is a fantastic winter destination.
Indoor exhibits range from good to awful, but I think OVERALL there are more bad ones than good ones. I would prefer northern zoos forget about tropical animals like gorillas and focus on snow leopards, takins, etc.
Conversely, I think warm climate zoos (like mine) should forget about snow leopards and red pandas and focus on savanna and desert and tropical animals (which my zoo does).