I have a set of fans in my Cuda that are thermostatically controlled with a fan thermostat in the intake. There is also a relay for each fan with the main power directly from the battery and the relay switch power to switched 12v power source.
I also recently installed an electric fan in my '92 Toyota truck. The fan has been hooked up to work both thermostatically with a probe in the radiator fins and able to be overridden with a manual switch. The probe works in conjunction with a controller that you can adjust the trigger temperature with a dial. On the Cuda, I would have to change the fan thermostat with a different one to adjust the temperature it activates at. The manual switch just bypasses the controller.
If you have A/C and a two speed set up for your fan/s or two fan, there can be a provision to hook a wire to your compressor wire to force activate the second fan or high speed when the A/C is on, just like the manual switch would.
Personally I like having the temp probe in the intake. It is clean and simple.