Roof prism binoculars have a more straight barrel shape and are more compact. In contrast, Porro prism binoculars have a more triangular assembly because they are made with Z-shaped prisms, and their objective lenses are located at a comparatively longer distance, resulting in a more triangular assembly. Moreover, Porro prism binoculars offer a wider field of view than the Roof prism binoculars.
Due to its sophisticated manufacturing process, the Roof prism is smaller and more expensive than the Porro prism. Last but not least, there is a subtle distinction in image quality between these two.
So, all in all, if you are a law enforcement agent looking over a large crowd, then it is better to opt for Porro prism binoculars due to their wide field of view, which will allow you to scan the crowd without much movement of your head. On the other hand, if you are surveilling a fixed position, you can go for the Roof prism binoculars.