Okay, here we go. Let me guide you through what I have learned. Stay away from the anolog ones unless you find it at bargain prices. I got the digital for several dollars more than the anolog. No brainer. Walker-san has the right idea, you want a two stage unit if you can afford it, ill get to that in a second. I have a Johnson Controls A419. Bought it along with a ferm wrap heating sheet and a thermowell for the temperature probe. My plan was to run the Johnson Control so that I could put my carboy in a fridge with the heat sheet wrapped around it. I wanted to control both heating and cooling at the same time.
When I got the unit I wired it up and discovered there is an electrical jumper that you need to put in one position to heat, or another position to cool. I can not do both at the same time
. Not a huge deal but my plan was to be spot on all year round. No guess work. I dont like the fact that I have to take the cover off to choose which mode I want. Other than that the Johnson Control is great. Since I have all the equipment and trying to get the end result I wanted I am going to buy a Ranco two stage Temperature Control Unit. They make a single stage Ranco that is like my Johnson Controls, But I am interested in the two stage. This will enable me to plug a heater into one socket and a fridge/cooler into the other socket. It can then be programmed for each to act in harmony of one another. I have a kegerator so I figure I will use my Johnson Controls for that since it is a simpler model.
The Ranco runs $99 dollars without being wired. You can buy it wired for $120. Might be worth buying wired since you need two female ends wired for the appliances. This requires more than just cutting an extension cord in half as I did for the Johnson Controls. I bought the Johnson Controls A 419 for $60 bucks which is roghly what you would pay for the anolog. So obviously you have options. You need to decide what your needs are. It might require you to fill a carboy with water and experiment around the house with finding different temperature ranges. All some people need it a chill spot in the basement and a ferm wrap around it to heat to temp. Others need to keep theirs in a fridge all year round to our friends out west. I hope my journey will help you decide.
Another thing is the instruction manual suggested 12 guage wiring be used for the unit. I went with this and it can be a little difficult to fiddle arond with stiff rigid wire in a tight little spot. Might wanna go with 14 gauge to make it easier on your blood pressure.