1. Importing Folders and Content allows you to maintain your folder structure that exists in Email Studio. However, content inside your Portfolio, My Contents, My Images, and My Documents is merged into the All Content folder in Content Builder. Any identically named child folder underneath those four legacy folders is merged into a single folder of that name. For example, if you have folders called Portfolio > Summer and My Contents > Summer, your content in Portfolio and My Contents appears in All Content, while your content in both Summer folders appears in a single Summer folder beneath All Content.
2. If you want to have more control over which content is sent to which destination folder, Importing Content Only is the best option. Users can choose one or more folders from their Email Studio folder structure to be placed in an individual folder created in Content Builder. No folder structure is imported with this option. The content from the selected Email Studio folders is placed in a single Content Builder folder. Users with permission to Create, Rename, and Move Content Builder destination folders from the Import Assistant.