Final answer:
The main difference between the coats of COPII and clathrin coated vesicles lies in their function and location in the endomembrane system.
Step-by-step explanation:
The main difference between the coats of COPII and clathrin coated vesicles lies in their function and location in the endomembrane system. COPII-coated vesicles are responsible for the transport of newly synthesized proteins from the endoplasmic reticulum (ER) to the Golgi apparatus. In contrast, clathrin-coated vesicles are involved in receptor-mediated endocytosis, which is the process of bringing extracellular substances into the cell through coated pits.