Around a decade ago, I had a dream. An actual middle of the night dream. An entire movie played in my head, all I had to do was write it down. I did a fair bit of research on the topic then I spent the next 10 years working it out in my head but not writing much of anything down.
Last year, I joined a writer's group and began the arduous task of writing a screenplay. I have no idea how to write a screenplay.
One of the other members of the group has actually written screenplays and had them produced. Her advice to me was: don't.
If you write a screenplay, she told me, best case scenario is a production company buys it and makes it into a movie. But when they buy it, the first thing they do is fire the writer. Suddenly, it's not yours anymore. They'll rewrite it and you'll never see a dime (or credit) beyond the initial payment.
But, if you write a book, no one can take that away from you. With luck, it will become a movie, and they will hire someone who knows the form to write the screenplay. You will always have credit and royalties. The story will belong to you forever.
Now I'm more than halfway through a novel and very happy with it. Maybe it will be a published book and then a movie someday.
My question is: How sound is this advice? Is it folly to write an original screenplay? Is adapting the movie in your head into a book the better choice?
Notes: I am aware of questions similar to mine (Should I be a Novel Writer or a Screenwriter? and Screenplay vs Novel) but they're more about career paths and how to choose which medium suits the story best. That's why I focused my question on the publishing issues involved in the choice, something the other questions didn't address (even if a few answers spoke of it).