Films are relatively short

Scripts are only one step

"The movie or TV show is the finished product; a screenplay is not.  Scripts are only one step in a complex chain of events leading to the final show or film."

Short stories will teach you to write

"Short stories will teach you to write. It's that easy. Short fiction requires a heightened focus on sharp storytelling and crafty writing. A novel lets you get lazy. Short stories demand you to write in tip-top shape. You'll learn to say more with less."

do both

"You can and perhaps should do both.  Novels and short stories combine together."

The View from the Cheap Seats

Always Be Writing

"Writers must produce.  And produce.  And produce.  ABW: 'Always Be Writing.' ... One book a year?  Psssh.  No.  Focus only on novels?  Not likely.  Writers are no longer as free to work in a single sphere of writerly existence.  Get used to writing short, long, script, game, non-fiction, etc."