I’ve visited both sides (as a tourist, not as a citizen of either country) and I preferred the view from the Canadian side. You can see all the falls from that side! If you actually want to experience the water and the mist, the US side is better but then you can always get the boat ride from the Canadian side!
PS: I proposed to my (now wife) while on the Maid of the Mist. It is an amazing experience. The roar of the water is deafening and you will get absolutely soaked, even with the plastic ponchos they hand out!over 4 years ago