Almost all toilets flush the same. The water leaves the tank and gravity takes it down the drain. The better toilets on the market like the Kohler and American Standard models have a two inch (2″) trapway that is glazed. Some of the other toilets on the market have smaller trapways and/or are not glazed. Obviously is the trap is smaller it will not pass objects very large. Having a glazed trap helps waste slide down the trapway. These two features are very important and should be looked for when purchasing a toilet. Most of the time a toilet with these features will cost more than a standard toilet but with the 1.6 gallon requirements its well worth it. Some of your other options include pressure flush and electric toilets. Val’s has a very quite and powerful Kohler electric toilet on display.