Admin AJAX vs REST API

Since REST API is comparatively new and offers better performance than admin-ajax.php, developers are now moving away from AJAX to REST API. You can read more about how they differ from the below resources:

• Comparing WordPress REST API Performance to admin-ajax.php
  • Testing showed REST API to be about 15% faster than AJAX API.
  • WordPress REST API versus Custom Request Handlers
  • WP REST API vs admin-ajax.php vs Must-Use Plugin: Handling AJAX Requests in WordPress