If you are using non-light-emitting heat sources like heat tape or heat rope or ceramic emitters to heat the interior, then your tightest control is with a proportional unit like Big Apple or Helix.
Ranco's are ON/OFF controllers with a differential that can be set I think as tight as 2 degrees. That is your next choice if you don't go with the proportional units above.
Those $30 analog controllers are ON/OFF with roughly 4 deg of differential. For colubrid eggs this is fine.
So in conclusion, here is my order of preference:
1. Any of the proportional units, whether GCS, Big Apple or Helix.
2. Ranco ON/OFF controller (single-stage heating)
3. Whatever else