Both services allow you to download orthophotos from different servers, using the same MDT command, but the main difference is in the resolution of the image obtained. WMS services usually have low resolution and only depend on the zoom we make in the drawing, and in the case of WMTS services you can choose the resolution factor, by default it is the one given by the zoom of the drawing, but it can be increased in several units depending on the server, and this will also increase the resolution, the size of the final image and the download time.