The Champion 4 uses a flapper. The orignial Champion tank flush valve has been recalled. The Cadet 3 uses a flapper too.
The Flapperless from Home Depot with the tray does't work all that well. Two of my friends have that one. I also had the Niagara for a few months in one of my homes.
Flushmate cartridges sometimes need replacement at 10 years, plus or minus. They still use a seal, and seals can go bad.
The old Mansfield Alto has a flush tower with a rubber seal on the bottom.