Same problem with Colloidal Silver sellers. You may as well get used to it.
The Best in my opinion is one where:
1. You Use No Chemicals
2. Produces the Highest PPM
3. Produces the smallest particle size
4. Where you do not end up with chemicals even though you do not start off with any.
While some do not start up with chemicals, they end up with chemicals for two reasons:
1. They use Tap Water
2. They use a magnetic stirrer that uses air as the catalyst.