I don't doubt your positive experience, Carol. However, brand name shouldn't make any difference as long as they are all based on conductivity, which is affected by many factors other than water.
I believe there are some very expensive moisture meters that some professional growers use that may be more accurate. However, they are far too expensive for houseplant use. That said, below is some information provided by the manufacturer of an expensive ($400) moisture meter that suggests some of the problems with meters in general.
1. Remove any obstruction to the soil that requires testing, such as surface soil, grass, leaves, pebbles, etc. If the soil is dry or contains too much fertilizer, sprinkle some water onto the soil and leave for 25-30 minutes before testing.
2. Before using the tester, be sure to thoroughly clean its metallic surface with a piece of whetting cloth. When using a brand-new tester, we advise you to insert it into the soil a few times before taking your reading. This is in order to remove any oily impurities from its metallic surface that may affect the accuracy of your soil pH or moisture reading.
3. Insert the meter directly into the soil that requires testing, embedding its metallic surface completely and tamping down the surrounding soil so that it adheres closely to the meter's metallic electrode surface.
About ten minutes after inserting the meter in the soil, the pointer will indicate the correct value of pH or moisture.
The meter may sometimes register different values depending on the soil condition, adhesion to the meter's metallic surface, moisture content, etc. Therefore it is advised you take an average of several measurements.
4. Press the white/green button and the pointer will indicate the correct moisture value.
5. After use, wipe the plates clean of soil or moisture.
1. Do not leave the metal part of the tester in the soil for too long (no longer than one hour) or it will damage the metallic surface.
2. Make sure the metallic surface is clean and dry before storing.
3. Do not use the tester near magnetic objects, and keep it away from other metallic objects.
4. Do not measure liquid. This tester is not designed for measuring liquid.
5. Do not hold the tester with fingers on the metallic surface. Fingerprints are greasy and reduce the flow of current.