The main benefit is the size of the saved page. The file will be smaller because binary resources (e.g. images) are not encoded in base 64 [1]. Moreover, the page and these resources are also compressed. The other benefit is that you can unzip the saved page and edit it more easily than a page saved with SingleFile because the saved page won't contain data URIs [2].

[1] https://en.wikipedia.org/wiki/Base64

[2] https://en.wikipedia.org/wiki/Data_URI_scheme