LibAnswers

Actually, they are a lot alike. Both permalinks (a type of URL, or Uniform Resource Locator) and DOIs (Digital Object Identifiers) are special kinds of addresses providing unique identifiers to artifacts on the web – ebooks, articles, infographics, etc. You can click on a permalink or DOI to go directly to the object to which it points. Both permalinks and DOIs are static and longlasting enough to be considered “permanent.” 

However, here's the important difference between them: Galen’s subscription databases and other library resources can dynamically generate permalinks for individual articles and other items at the user’s request. DOIs, on the other hand, are assigned by a registration agency called the International DOI Foundation. According to APA style, both permalinks and DOIs may be used as identifiers in reference citations – but only one or the other at a time. For information on when to use which, see https://apastyle.apa.org/style-grammar-guidelines/references/dois-urls.