How can we determine which is a good water purifier for home drinking water purposes?

Why do you ask? If you're looking for a distiller to remove minerals from the drinking water that is supplied for your community, I'd reconsider. Epidemiologic studies generate a huge amount of junk by their very nature, and the "theory" that these folks site seems misguided -- ask a junior-college level science teacher. In an emergency / possible contamination situation, nothing replaces boiling.