Prose writing and screenwriting has a bit in common. Obviously they both involve writing. More importantly they both involve telling a story. But they tell their stories very differently. There are some things prose can do that screenplays cannot, and vice versa.
I will use the memoir I wrote as an example to illustrate what I wrote.
In many ways, my memoir wouldn’t work as a film. The story takes place over two days, and not much happens. It’s a lot of observations from former and current me, and a lot of introspection. This doesn’t really work on the screen. Voice over narrations are used sometimes to give inner thoughts in movies, but it’s not a popular filmic convention. Cinema is a more dynamic medium than the written word, due to its audio and visual aspects. While a longwinded inner monologue might work on the page (not saying mine do), they would not work on film. On film, it’d be extremely dull. And if the whole film featured constant inner observations, it’d be kind of repetitive and overbearing. And it’d get in the way of what’s happening.
And that’s where there’s another difference. In a film you can just show what’s happening. But in a written work, you have to tell. The goal is still to show with writing, but at the end of the day, you’re still just telling while a film is literally showing. So while a film version of my story would lose my keen observations, they wouldn’t all be needed.
Ultimately, a film of my memoir would lose much of the connection to my character, as I’m in simple experiences, with the deeper meanings being divulged through my thoughts. So a successful adaptation would need additional scenes to show the necessary development of my character. Which would be fabricated. So the movie would lose some authenticity. But the movie could add things to existing scenes. There isn’t much tension in my story. Just a small tale with a small change in my character. And I had a hard time writing that. What am I supposed to say?: “I hated my job before and I didn’t like having to lifeguard when kids were in the pool, but now I think talking to kids and other people at work is rather enjoyable.” No subtlety in that. I have to contort to make it feel natural and not be overbearing or heavy-handed with the lesson. So I had to say that I talked with a kid and that I enjoyed it or whatever (I wrote it better then than now). But in a movie, you’d be able to see me change while talking to this kid. You’d be able to see from my face and my body reactions how I felt about the conversation. And a musical score would add some emotion that I don’t think I could ever convey in my writing.
Anyway, both prose writing and screenwriting have their strengths and weaknesses. Objectively, neither is inherently better (subjectively screenwriting is at least 100% better), but one might be better to tell a specific story than the other. But I think both could successfully tell any story. Because they’re both great. The end.