Sometimes I run traditional location-based adventures that make use of a predefined, keyed map. Other times I run "scene" or "event"-based adventures. (Most adventures even manage to combine both.) To be honest, I don't find them to be all that different as modes of adventure in terms of preparation or execution.
There are a lot of strange assumptions that orbit the notion of "scene" and "event"-based play. I've seen accusations that these styles of adventure are "scripted," as in they provide a predetermined plot line into which the DM merely inserts the player characters. This assumption often implies that the players have little or no agency and must follow the DM's "story" as it was envisioned at its creation.
I don't find that assumption to be particularly accurate in terms of how I prepare for game sessions or how they play out at the table. Here's why:
When I prepare for a scene or event-based game session, I only prep a situation--something that happens that will draw-in the player characters, a problem to be solved (or not) by the players' actions, something that demands confrontation.
Think of a situation as a question, but consider that posing a question doesn't presuppose a known answer. I think this is what people mean when they say "Play to find out what happens."
The shape of the adventure is a series of "scenes" or "events" that I have prepped ahead of time. In more concrete terms, this means I have prepared places they might visit, NPCs they might interact with, and fights they might get into.
However, it's important to emphasize that none of these events or scenes have to be played out necessarily for the game to progress. It's also worth noting that I don't plan how these scenes or events will resolve--that's in the hands of the players as they make decisions for their characters and sometimes determined by how the dice land if it comes to that.
In this way, an scene-based adventure does have a certain shape, but the shape is malleable and definitely not predetermined. In fact, the choices the players make inevitably change the shape of the adventure because the actions their characters take have consequences; the world reacts to the characters, the situation changes in response
If the players decide on a course of action I didn't see coming...I improvise. There is no urge to get them back on track; I'm happy to go where they lead. There is no plot to be followed and no story that needs to arrive at a foregone conclusion; rather, there is a web of connections to be navigated as the players choose.
The web of connections is there in the corridors, intersections, a stairs; it too is to be navigated as the players choose. The web of connections is present in every hexcrawl; each border is defines the shape and scope, each numbered hex points to scenes to come or to be skirted at the players' decisions. Admittedly, my scene-based adventures tend to use a lot less graph paper than my location-based ones.