As you can see most people are going to tell you that there's not much difference between Ranco and Johnson thermostats. Feature wise the Johnson offers a couple of extra settings that the Ranco doesn't and the Johnson has night drop capability.
We have been using both brands for over six years and over 80% of our Rancos have failed. We haven't experience any failures with the Johnsons.
Needless to say the only brand of on/off thermostat we buy now is Johnson.