When should I use observable subscriptions instead of regular variables in an angular template parameter?

The reason for the repeated console logs is due to Angular's default change detection system. This is why you can use a property or method in your component to signal the load event.

If you utilize observables to handle asynchronous events, then you can update your component's change detection strategy to something more optimized. (See https://angular.io/api/core/ChangeDetectionStrategy)

If your app is small, then the performance improvement is negligible. However, if you are working on a larger, or more data intensive application, then you may want to have your components utilize observables and OnPush change detection strategies.