Lately, I found out that Application Launcher also features all the functionality I use from KRunner.

In my particular experience, Application Launcher is snappier at first launch and also returns results rather quickly. For me, this begs an obvious question.

What's the use case for using KRunner over the Application Launcher?

So far I've noticed that pressing Enter on the Calculator results makes the entry be copied on KRunner, but this does not happen for the Application Launcher. I'm certain there must be something else to it, otherwise people would not be using it (even I found myself using it from time to time, but could not understand why).