If you use an external controller then the lower part will be controlled by the controller at the set temperature. The upper part will be somewhat cooler being that the coils are located there but will no longer freeze. I like to use freezers with a controller because the whole interior is open and is the same temperature if the air is circulated.
Fermentor 1: Bill's House Ale II, Fermentor 2: German Helles, Fermentor 3: Bill's Schworzbier (Black Bier)
Tap 1: Bill's House Ale II, Tap 2: German Hefewizen, Tap 3: Nut Brown Ale
Future Brews: Stone IPA Clone, Blonde Ale, Budvar Clone, Newcastle Clone
New toy: Blichmann 27 gallon fermentor
If you find yourself in a hole, the first thing to do is stop digging
Good judgment comes from experience, and a lotta that comes from bad judgment