The same elements to write a long story is used when composing poetry. I ask the same essential questions of my poetry and those are the who, what, when, where, and why.
As to subject matter, to me, it is easier to relate to what I am writing about in poetry as I am able to focus on one theme or story-line.
For instance: it would be hard to write a full short-story about the tail of one of my cats, but I can take that same cat's tail and create a humorous situation which has the short story beginning, middle, and ending. I can add conflict and resolution. When I write, his tail is constantly switching back and forth across my face. Heaven forbid if I should move him from his favorite spot on the sofa to get him to stop.
In poetry, you are able to get to the heart of the story quicker.
I enjoy writing short stories if I want to take my reader more in depth into the minds of my characters, give them more details, and take them on the scenic route of words.
Express way or scenic route? Either way you are writing.