It's a Bird! It's a Plane! It's a Medium for Storytelling!
Story is story, but the medium is everything.
You have a great story, right? It's about a girl who gets swept up in a tornado and taken to Munchkin Land. She has to find some Wizard, in order to get her butt home. You should totally write this story. But should you write it as a book, a movie, a TV series, a play, a webisode, or what? In my opinion, the answer should never be, "Whichever I feel like writing!"
The medium you choose matters.
"Friends" is perfect as a TV series. Can you imagine it as a movie? They would have to find one set of story lines and drag it out over 90-120 minutes. "Friends" is not about much- it's about characters and the different experiences they have- perfect for a TV series: you have different experiences each episode.
Now imagine "Titanic" as a TV series. What would the episodes be about? Would each episode be about people trying not to drown? Or would it be about Rose trying to escape her family's clutches? I'm not sure how you would do that episode after episode, season after season. When exactly would the ship sink? Would it?
If you have a story about a girl who gets swept away by a tornado and has to find the Wizard, I would think it's because you really want to get her home in the end, and show how she's grown. But that's not what a TV series does. A TV series can (hopefully) go on and on for years. Would she ever get to the Wizard?
A TV series, however, works well for ongoing issues: things that can have different iterations every week (so to speak.) Police shows work perfectly for TV because you can have the same cops handling different crimes every week. Or a show like The Wire, where they're dealing with the same criminals the whole season, but we know a whole other crime can be thrown their way if you get picked up for season 2.
If your story has a clear end, and depends on its end for its all over greatness, then an episodic TV series is probably not your jam. Feature films have a clear beginning, middle, end end in 90-120 minutes.
What about a limited series, or webisodes? A limited series is very different from an episodic one. A limited series is much more like a feature film, as it has a limited number of episodes that come to a pre-determined end. The Bodyguard is a limited series on Netflix. Often times, a limited series is chosen over a feature format because a limited series allows for more time. In other words, "The Bodyguard" is six episodes, five of which are an hour, and the final one 75 minutes. If it were a movie, that would be a 7 hour and 15 minute movie, which is even longer than "The Irishman!" Webisodes are good for brief moments of story, much like a TV series, though perhaps much, much shorter. Webisodes, being that they're online, can often be much easier and cheaper to make. You could make a webseries today! With no money! (But buy your actors lunch. Always buy them lunch.)
Once you've chosen the right medium for your story, you have to write it. But if you're writing a screenplay, write it like a screenplay. If you're writing a play, write it like a play. They are not the same thing.
Story is story, no matter where you go. Sure, the story in an episodic TV series is a bit different from that of a feature film, but story is story, no matter if it's a movie, a play, a book, or a webisode. Format, however, ranges greatly.
If you've worked with me on a screenplay, you might know I'm a stickler for formatting rules. This isn't because I think a reader will hate your script because you didn't write a slug line correctly; it's because you have only one chance to make a first impression, and you don't want that impression to be, "This person doesn't know how to write a screenplay."
If you're a talented novelist, great! But that doesn't mean you know how write a stage play. If you're a talented playwright, terrific! But that doesn't mean you know how to write a movie.
Though what I'm saying is probably pretty obvious to most of you, I'll give you an example: when writing a novel, you can spend three pages describing the decor in a restaurant. When writing a movie, you probably shouldn't use more than a line or two. If you look at a bunch of plays, you'll see the format differs somewhat between them: some have the character's name centered; some have it aligned to the left. But in screenplays, there's basically a right way and a not-right way to do it.
It matters what your screenplay looks like. It matters how long you take to describe a restaurant. It matters where the character's name goes.
Don't wear a halloween costume to Passover. Don't sing Hanukkah songs on Easter. And don't wear a white dress when you're a guest at a wedding (you don't want other guests saying, "This mother-of-the-groom doesn't know how to write a screenplay.")
When writing a play, write it as a play. When writing a screenplay, write it as a screenplay. Don't know how? There are a number of books on the topic, you can watch one of my free videos on YouTube, join me at our Writers Workshop, get my Awesome Screenwriting Outline and Screenwriting Handbook, or book a 1-on-1 session with me.