I'm definitely more of a Facilitator GM. The games I run are far from the stereotype of kids in a basement in wizard costumes. When I play its in a pub and generally quite casual. That's not to say we don't sometimes have groups with grid maps and miniatures but the majority of the time there isn't the room for high levels of prep to be brought.

One thing I have learnt from over prepping is that players will go out of their way to destroy anything you had planned anyway. You need to have light ideas that are flexible and can be reused if part of the story goes off tracks.

Have a general idea of what you want to accomplish in the session and see what happens.

On the other hand one shots differ from a campaign. In a one shot I will plan like a storyteller and make sure players feel like they got someone out of just the single session even if it was just an excuse to get drunk.