Thanks for the question!
Let’s say there is a component that displays the number of items in the shopping cart. That should be integrated in a web page that shows product details. The product detail page is usable without the number of items in the shopping cart.
Let’s assume this shopping cart component fails. With client-side integration, the component will just not be loaded and the page shows otherwise OK. With server-side integration, you will need to handle the failing service and make sure the rest of the page is displayed.
If the shopping cart was needed to show the page, this isn’t a problem any more: If the shopping cart component fails, the page will just not be shown. Actually it is harder to ensure the page is not shown with client-side integration. So server-side integration is preferable if the component is needed to show the page.
Let me know if you have any other questions!