Pretty much any food in Canada is expensive. Fallsview is the nicest Casino there, but Seneca Niagara has some really nice rooms. What games will you be playing? The three casinos all differ greatly depending on what you play. But if you don't mind a little walk, they really aren't too far apart. Or you can drive back and forth across the bridge, depending on the traffic. The views of the falls are best from Canada if that is part of your decision. Don't forget to get a players card in the Canadian casinos and put a few dollars on the tables or through the machines. Then when you leave the parking garage, show your card and parking is free. Otherwise it's about 20 or 25 bucks. Parking in the Seneca casino is always free.
As long as you don't mind the cost, the casinos have nice hotels, but if you want to save a few bucks, there are plenty of other places to stay cheaper. If you are looking to do anything besides gambling and if you've never been to the falls, drop me an e-mail about what you're looking for and I will try to help.