Zu etwas (ein-)laden

I am a bit surprised that I have not found a lot of discussion regarding the difference of the German expressions "jemanden zu einer Veranstaltung einladen" vs. "jemanden zu einer Veranstaltung laden" (both: inviting someone to an event). Recently, I was asked by a non-native speaker if there is an "ein" missing in a sentence and I said "No, you can also say 'wir laden zu der Eröffnung'" but while explaining the difference I began to struggle. In general, it is sufficient to google something like "selbst selber" in order to find a bunch of blogs and forums discussing the appropriate use and understanding of such similar but not equivalent words (whether from language learners or from a ordo-linguistical view). But in this case: Nothing. Just a small article in the German standard ortography dictionary Duden, stating that "laden" is exalted. This is certainly the case, but is this anything to say about this pair of words, especially if you are learning German?