The Gentle Reader will take note that most of what I speak about applies to novels, and not to short stories. A "short" story is one that is typically no more than 2,000 words, and at its best contains one, maybe two characters, a single setting and one resolution. The focus of the story is intended to highlight the sharpened facet of a theme, and to do it well, or in the very least to tell a tale that will be memorable to the reader. Traditionally, from Aesop to O. Henry, they tended to end in a moral; O. Henry employed the 'twist' ending, arguably better than anyone else up to his time. If you are unfamiliar with O. Henry, and you have an interest in avoiding cliches where the twist is used, I recommend him.
I used to write short stories, and had some luck with them. If you will do a lot of reader's theatre, where you have the opportunity to read aloud in a coffee shop or such, something about 1,200 words is good. Humor is better than something poignant, as it gets a crowd going. But humor is hard to write, and most short stories you will hear are rather unremarkable stories about people's families, or places they've traveled, or some moderately unusual thing they experienced which they decided to write out as a story. These are dull to read, and worse to sit and listen to read aloud, particularly if the writer doesn't have a performance voice. A monotonously written story read with a monotonous voice can equal 12 minutes of death.
I have very rarely heard a short story read aloud that I enjoyed that was not written by some master at least 50 years ago. For years I wrote them, but I've never especially enjoyed reading them. Those that I've written have little value, as short stories are not published and when they are, they usually don't make any money. I wrote a series of humorous stories for a magazine for several years that paid me a fair 30 cents a word, but that was because they had a trade angle - home renovations. They were not what could be called pure fiction.
I don't like reading short stories, as they end quickly and this means I must make the effort to start again with new characters. Somehow, I've never enjoyed starting anything. Most of the time, it takes ten or twenty pages for me to start to care about the characters, and by then, the short story is over.
Overall, I prefer the difficulty, the depth, the effort of writing a novel, even if many novels that I've started never saw an end. I am unsatisfied with characters in a short story; I want to give them a greater purpose, and let them talk as much as they wish. As such, it is very rare that a short story occurs to me that I take the time to write down. I would rather conjecture for several months about something I haven't started, than write something which I then forget about by the end of the day.