I lived in Niagara Falls NY for 25+ years and still work there every day. The deal for the Niagara Parks pass is pretty good - the Maid of the Mist is 14.50 CA and 13.50 US by itself. The other tours are good - it will be a full day of site seeing if you do the pass. If you don't do ALL the tours, though, it's not that good - but they are all great, especially Maid of the Mist (a MUST do). If you're planning on staying in the Falls overnight (which is what most people do), check prices on staying on the American side vs Canadian side - Canada is much more expensive, especially eating. However, to be fair, the American side is not as nice for things to do as the Canadian side. Canada has lots of touristy things - wax museum, daredevil museum, spectacular gardens/parks, etc. The American side has a very nice park and you can get very close to the Falls itself - but except for the park and the casino and the fashion outlet mall, there's not much to do. On the Canadian side, you generally must view the Falls from across the river - which is absolutely beautiful. The American side doesn't offer the view that Canada does. Also, to be fair and to warn you, much of the American side is really slummy, especially near the tourist area. Don't walk away (OK to drive) from the tourist area and do not leave anything in your car that might be something someone would want to steal. It's OK to walk around in tourist area, but don't do it late at night except right at the casino. They have good security. There's a reason I moved to the suburbs . . .
If you like to gamble, you will want to visit the American side - the Canadian casino is more expensive and the odds aren't as good. The Seneca Nation of Indians has a beautiful hotel on the American side with great restaurants inside the casino complex. The Canadian casino is very nice, also, and the area surrounding the Canadian side is MUCH nicer than the American side.
So, there are reasons to go to USA, but you might not care and want to stay in Canada. Whichever you choose, enjoy your stay (we're all natural born tourist operators here - always promoting!).