Service Portal offers an alternative user experience to the standard platform User Interface. It is easy to configure, customize & extend . it is similar to what users are used in other consumer products.Service Portal is a simple way to configure an intuitive interface for the users. It interacts with the underlying ServiceNow platform, so you can access any of the platform components in the portal.
Service Portal serves to address all of the pain points combined with CMS. It’s a simple but more delightful experience with different levels of configuration. Basic users with less technical ability can assemble a simple site, while more advanced users can configure themes, widgets & pages.
Service Portal comes with widgets for various components such as Knowledge, Catalog & Incidents. the underlying part of CMS site can use those components to migrate over without complete re-implementation. The migration effort may vary depending on the customizations made to components.