I believe you want to compare performing image processing and classification using a MATLAB script or using a Simulink model.
Using a MATLAB script, the goal is typically to process the images as fast as your computer can. You have input data, and you want to know the result (for example, classified images).
Using a Simulink simulation model, the goal is typically to develop a controller that can process the images in real-time. You do not provide it all input data at once, but the model samples input data from a camera for example. It processes the images from the camera and outputs results (for example, classified frames).