On public-facing websites using cross-site publishing use the Catalog Item Rank Model rather than the Default Search Model to get more relevant search results.
When using search-driven publishing and building content aggregations you can choose to display content based on its relevance rather than using fixed sorting such as by date. In such cases the selected Search Rank Model determines what piece of content will be displayed on top. SharePoint 2013 contains a number of Rank Models. The one it uses by default is good for collaboration scenarios as it promotes content based on its filename, author or social tags. When using cross-site publishing the Catalog Item Rank Model is more likely to offer more relevant results as it allows you to rank your content not only by the standard properties such as title or body but also based on the type of content as defined in the catalog.