When sourcing a mobile banquet truck, prioritize high-grade stainless steel (SUS 304) for the body to ensure corrosion resistance and food safety. The insulation layer should be made of high-density polyurethane or rock wool to maintain internal temperatures for at least 2-4 hours. For heated models, ensure the heating element is equipped with a precise digital thermostat and a humidity control system to prevent food from drying out. Additionally, check the load capacity of the casters; they should be heavy-duty, non-marking, and equipped with locking brakes to handle weights exceeding 200kg safely.