I haven’t had to replace a toilet, but if I one day do, I’ll be heeding Galen from Rain City Guide’s advice on low flows for older homes:
Low flow toilets and old houses
Consumer Reports clearly does not have an old house that has charmingly rust-flecked, low pressure water. See, the Flushmate system works by storing up pressure from the pipes in a sealed tank and uses that pressure to forcefully push water out when you flush. There is no need to rely on gravity to move water through Flushmate toilets, although there are no mentions of them being used in space on the internet. When you put one of these suckers in a house with rusty pipes . . .