I used to write lots of short stories when I was a child (from when I could more or less write stories until the age of 14), but if I write short stories now they usually end up being the outlines of a novel or the first draft of a novella rather than a few thousand words short story. Then I only remember it was supposed to be a short story when I'm halfway through the second draft of a novel... Oh well...
I prefer the short story because they are generally less of a daunting task than a full blown novel. Like my current project for instance, I call it a "novel" but in reality it's more of a compilation of short stories that are all related to one another, and set in chronological order, yet not in the sense of how a novels chapters relate to one another if that makes any sense at all.
Write what you want, a bad short story doesn't differ from a bad novel. You'll learn from your mistakes from both. (Assuming one's first story is bad) When I first figured I wanted to write I wanted it big, then it went from big to massive. My story matured a lot since then. I got a better grasp of good stories and bad stories, big nono's, wannabe ripoffs and simply unoriginal stuff ( Thanks to the size) My story went from a 0/10 to a perhaps....I don't want to sound too confident, 7/10 or perhaps 8, (one wouldn't write something that you think is bad right?) so yeah, I thank my story's huuuuge improvement to the size, if I limited my mind and imaginary to a short story I'm pretty sure I wouldn't be near the "skill" I have now. I'll assume with a good reason that all stories improve as the writer improves and learns common errors, flaws and realistic ways of writing what they want to write (assuming one takes the time to research and want to learn, as well as to sit down and inspect your own story)
I personally have not found a way to write an entire novel so all of my work is short stories! I still like every story I write though
While there are some crossover skills developed by writing short stories and then moving to novels, the structure and pacing and overall complexity makes a novel a far different undertaking. A short story isn't a 'chapter' except in that it might be about the same length as a chapter. How a writer goes about description, characterization (both direct and indirect), use of dialogue and many other aspects varies greatly. Maybe a good (okay, adequate) analogy would be comparing cross country skiing and down hill skiing. Both take place on snow and involve travelling over it. They use some of the same muscles and balance, but to a different degree, and they require some of the same equipment, but structured differently and often for different purposes. Because one has mastered downhill skiing doesn't mean that same individual is a master of cross country skiing--but he/she may have a leg up on trying the new version based on previous experience.
