There are a few differences:
The manual version will have a blue or brown transformer, a single speed loom assembly (that activates the pump) and a shower valve (cartridge) that has a blue collar on the front. The manual cartridge does not have the failsafe feature should one of your water supplies fail.
The Thermostatic model will have a black transformer, two speed loom assembly and the cartridge will gave a grey tempertaure collar on the front.
For ease of identification, the manual model has the words "on /off" written on the on off control knob and just has red and blue markings for the temperature.
The thermo model has the words "Boost , On , Off" on the control knob and numbers 1-8 above the temperature lever to indicate hot and cold settings.
Hope this helps.
G-Man, April 2009
