I have two temp controllers. A A419 Johnson controller, and a STC 1000. I use the A419 Johnson controller on the fermenting refrigerator and the STC 1000 on the chest freezer Kegger.
I bought the STC 1000 first because it was cheaper and it has been working fine. A couple of Cons - 1) It only reads out in Centigrade so you need to convert to Fahrenheit. 2) You also need to splice it into the electrics for the device you are trying to control. So in my case that means I no longer use the thermostat that was part of the original freezer. You will need some basic electrical skills to make this work and you will probably want a box to mount the STC 1000 in, I used a project box from radio shack. Picture is the STC 1000 on my kegger
The Johnson A419 is a plug in device. you plug the fridge into the A419 and then plug the A419 into the wall socket. This means there are no direct wiring changes to the fridge. This device also comes with its own thermostat but since the fermenter will be used at a higher temp than the normal fridge temp there is no need to disconnect the original equipment thermostat. Then if you want the fermenter to go back to being a fridge, you just unplug the A419 and plug the fridge into the wall socket and it will operate as normal. It reads in F so no conversion needed. Cons - It cost more.
