Johnson Temp controller differences

I was hoping to find out if anyone knows the differences between the different Johnson A419 controllers? I have seen blue ones, grey ones, and different part numbers for different grey ones. Are the differences a wash or do they matter?

Some of the A419 controllers have the temp probe fixed to the bottom of the controller others don't provide a temp probe and are digital. Grey I believe are analog. I may stand corrected but gives you a start.

Blue are pre-wired, plug n' play. The gray ones are not wired. Different part numbers equal differing voltages. Both are digital. The ones with the copper probe are analog. Here's more info than you probably need.
http://cgproducts.johnsoncontrols.com/MET_PDF/125188.PDF

If you're looking for a temp controller, you might consider those that control two devices - your freezer (or refrigerator) and heater. Here are a couple of url's for such products from Amazon. I use the Control Products TC-9102D-HV to control my chest freezer and the heating element I put in there with my fermenting beer. I find this device keeps my product at +/- 1 deg. F. At $60, the price is decent. Have also heard good things about the STC-1000 which sells for less than half that and is probably easier to operate.

http://www.amazon.com/dp/B0057APR3I/?tag=skimlinks_replacement-20

http://www.amazon.com/dp/B00862G3TQ/?tag=skimlinks_replacement-20