@Ziggurat @rpg In my experience it's not a matter of preparing more or less but how you prepare. When I started out in the hobby I used to do very detailed scripts in preparation almost like a choose your own adventure game but work with much broader strokes these days and playing PBTA games very likely helped in that.
I like to prepare situations and characters. A situation describes some event that is happening or could happen, a conflict of some kind. "Bandits attach the bishop's carriage". Characters are usually a short description "Guard" and a motivation "Impress the captain".
The rest flows from this and lets me easily pull from prepared stuff when improvising.
I keep these noted down for each session and prepare along what I think the next story beats will be. I rarely end up using all but then simply move them along into the next session or into the archive of ideas that could be used later.