GMing notes: Impromptu gaming vs Prepared material [crossposted to Pathfinder et al

If Im running an improvised game or a prefab adventure, the performance is mainly for the players , and its on me to do a good job. But if I'm running a game which I've previously written to play test it, the game becomes a lot more interesting for me as a GM. Running a game for a play test, I'm personally interested in representing the material effectively because I've written it myself , and I'm much more intrigued by what actions the players take in response to the various obstacles I've placed because they tell me about what ways I need to revise the material. Realistically , running a game this way is more time consuming... Its more efficient to run a game impromptu style, but its much more interesting to me, personally, to run material I've written in detail. I used to see this practice as a weakness because its inefficient from a perspective where the game is the only end goal, but if the end goal is to produce original content then this is not an inefficient method. I'm simply not interested enough in running the game for fun to care much about a game where I improvise everything. If I wanted to play for fun, I would just play as a character. For me, there has to be a creative goal.