Calling fridge nerds.

My boss bought a trailer a couple of weeks ago, I have used this for one reason or another this week.
It differs to mine as it is a twin evap one.
What I noticed was it was more efficient on cycles mode than mine is on constant.
Is the most efficient way of running this fridge to use the rear evap, or do you keep the rear switched off.
I'm talking single temp jobs, which it will do 99% of the time.
If I take a -25 single temp load, what is the most efficient way of doing it?
If I take a +3 single temp load, etc?

None ojf us really know, all our trailers are single evap.

The trailer is the latest model Schimtz Cargo bull with TK fridge, ( not sure the model sorry ).