Extra and Divi serve two different purposes. Extra was designed with blogging and publishing in mind. It’s great for magazines and blogs. Divi Extras Nulled is more of an all-purpose theme and is great for creating websites in general.
Divi is also a good choice for blogging and publishing but Extra has a few modules in its Category Builder that make it stand apart as a publishing theme.
Wouldn’t it be interesting to use Extra’s Category Builder Modules in any Divi page or post? That’s what a third-party plugin called Divi Extras GPL does.
Divi Extras Free Download doesn’t turn Divi into Extra. It doesn’t give you access to the Category Builder or the post features such as the options, review system, related posts, WooCommerce, etc. For more information comparing Divi and Extra, see the article Divi vs Extra – How to Choose Which is Best for Your Website.