The primary difference between the US and Canadian sides of Niagara Falls is the perspective and the atmosphere. The Canadian side (Ontario) is famous for offering the best "panoramic" views, as you are directly facing the massive Horseshoe Falls, which is the largest and most impressive of the three. The Canadian town is also very commercialized, featuring high-rise hotels, casinos, and a "Vegas-style" entertainment district (Clifton Hill). In contrast, the US side (New York) is situated within Niagara Falls State Park, the oldest state park in the country. It offers a much more natural, "green" environment with wooded walking paths and islands. While you mostly get "lateral" views of the falls from the US side, it allows you to get much physically closer to the rushing water, particularly at places like Terrapin Point or the Cave of the Winds. Essentially, you go to the Canadian side for the "big picture" postcard views and the US side to feel the raw power of the water in a more serene, park-like setting.