The American standard Cadet II is the crown jewel of low flow gravity flush toilets! It uses the same amount of water but has a 1/2 inch wider flush port than the others so waste hangs up less. I like the look and the design of the Kohler wellworth as well but I always move the little yellow sponge float lower in the tank so that it flushes harder. A have never liked the idea of having to hold the handle down. Both brands are gold standard, I don't think that you can go wrong. Just whatever you do, don't buy the Mansfield 1.6 gpf gravity flush. It's worthless.