1st. watch caps lock, conveys SHOUTING.
To your question, it depends. Where are the doors relative to each other? Relative to the space (along long or short wall)?
What type of heater(s) are you going to use?
What does your budget allow?
What does the client want/need?
How much space is available? Watch for conflicts with lights, structure, fire protection.
Where/how is product being stored/staged on the loading dock?
Evaluation of these questions and others have to be taken into consideration; it is your job to evaluate different options along with each option's pros and cons.
I could make one or two heaters the better option depending how the above questions are answered.