As for the "Canadian side" is better, to each their own, Tribe makes some good points on the views although as someone who has been to the falls 50 times + we've spent 95% of it on the Canadian side.
But don't get confused, as for Niagara Falls the city, you don't want to be messing around on the American side at all, as far as staying or trying to do activities. It's pretty awful, although I'll make an exception that you could get a better pizza on the American side if you want a bite to eat. But if you're spending any time on the American side, do it in Buffalo, not Niagara falls.
While I'm a one day in the falls at most type of guy (and I admit that familiarity probably plays into it a lot), I would not try to spend the day there and then stay in Toronto. While it's a short drive distance wise, traffic can be an absolute nightmare, and then you're dealing with big city traffic when you hit Toronto. You could get in your car at say 7-8pm after an exhausting day in the Falls, and easily not hit your room until close to midnight. Or it might be fine, but after my last time I made the trip, I wouldn't plan that. And the route in between isn't like taking the American Interstate, where you can just pull off anywhere for something to eat or to use the bathroom, etc. A lot of nothing in between, and the last time I went it was practically bumper to bumper stop and go traffic from the falls to Toronto.
Staying at the Hilton in Niagara Falls is fine, if you want to get a look at it in the morning, and it would give you a chance to maybe check it out before quite so many tourists are crowding.
