Federated access focuses on 'meeting the user where they are', meeting the user expectation of being able to navigate to a resource from the open web and gain access; without having then to retrace their steps to a library discovery tool to gain access or use a tool such as a VPN to gain access.
Using federated SSO offers a fairly standardized experience when navigating to a vendor or publisher site, locating the institutional login and signing in. For example, vendors and publishers using Seamless Access offer a recognizable institutional login workflow.
SSO allows for obtaining granular usage statistics (without releasing any personally identifiable information); at department, or group level, for example. This isn’t possible with IP access. Federated SSO also allows limiting access to a resource for specific groups, where they are only licensed to provide access for one department for example.
Federated offers single sign-on not only to the content but also any personalization services offered by the website e.g. CPD/CME credits (continual professional development/ Continuing Medical Education), bookshelves, etc. When using IP recognition a user would usually have to provider more PII (personally identifiable information) and manually sign-in to each site separately.