The difference is that the base64 is inline, which means the browser won't have to fetch one extra asset (the same reason why you concatenate CSS and JS into one file each).
@fernkul Hmm, that's true. So I am not entirely sure how to answer that, but I would guess you might be able to save bytes after zipping? Might be worth to check that one out, huh :)
https://codepen.io/yoksel/details/JDqvs/ maybe that explains why some use it at least that's the only valuable input about it I found. The next thing that comes to mind is that i don't know how path operations are working on the base64 encoded version but I did not really took my time to look into it.