Both WPBakery and Visual Composer are products from the same team. Before WPBakery came into existence, it used to be a Visual Composer later the product was renamed to WPBakery on the CodeCanyon marketplace and Visual Composer became a more comprehensive independent WordPress website builder.
Visual Composer Vs WPBakery: How They Are Different?
As already mentioned, both these products are from the same team and you will find a lot of similarities between the two products.
However, the core difference is that Visual Composer is a complete website builder that will allow creating a complete website from the scratch on the other hand WPBakery is a page builder that allows you to create pages with custom layouts and elements.
So, if you are looking for a more comprehensive option, Visual Composer is the product you need.
With Visual Composer, you can create a complete website with a custom header, footer as well as sidebar and it will overwrite the default theme design.