The advantage of writing a motion picture is that the studio can afford to get you the biggest stars and directors available, and the budgets are enormous. The disadvantage is that it takes a movie about two years to reach the screen, and after a few weeks it disappears. The advantage of writing for television is that if you create a hit series, you can watch it every week for years. The disadvantage is that television shows have a limited budget, which means that you may not be able to get the actors or directors you would like. Writing for Broadway is interesting.
Playwrights get very small advances, but they own a piece of the play.
On opening night, in a white knuckle two hours, you learn that you have either wasted two or three years or that you have become a millionaire. Of all the mediums I've worked in, I prefer writing novels. The other forms are collaborations. Cut some scenes. There is no one to second-guess you.