Personal preference, second choice, and then simply own the choice and communicate it that way.
Example, take the view that you want to make your writing like Hemmingway. The below is from his views on writing "icebergs", where the point is avoid all unnecessary padding, and then avoid what other authors would consider "standard" padding:
If a writer of prose knows enough of what he is writing about he may omit things that he knows and the reader, if the writer is writing truly enough, will have a feeling of those things as strongly as though the writer had stated them. The dignity of movement of an ice-berg is due to only one-eighth of it being above water. A writer who omits things because he does not know them only makes hollow places in his writing. —Ernest Hemingway in "Death in the Afternoon"
Or as the New York Times put it, write:
gripping, lean, hard, athletic narrative prose
Or the way that Carlos Baker would describe that style:
get the most from the least, prune language, multiply intensities and tell nothing but the truth in a way that allows for telling more than the truth.
Depending on the publisher, this idea can then probably be pitched, with a cover letter, or other explanatory method, to help the reviewer orient. Many of the publishers, such as Penguin, have lines, and you could sell the concept as short, concise fantasy, with a lean writing style.
The "Dresden Files" might be considered to fall at least somewhat into this category among contemporary fantasy fiction. Short, focus on the main plot, don't waste a lot of time with exposition, padding, or overly length descriptions. "Here to tell a supernatural detective story, that is what is accomplished."
As reference, 40k is on the short side, yet not unreasonable. Examples:
- The Lion, The Witch, and the Wardrobe, 38,421, Fantasy
- The Time Machine, 32,149, Apocalyptic Sci-Fi
- The Tombs of Atuan, 45,939, Fantasy
- Fahrenheit 451, 46,118, Dystopian Near-Future Sci-Fi
- Animal Farm, 29,966, Beast Fable
There's a decent number of well written works in this length range, that still feel acceptably long, and in some cases, such as Animal Farm, also manage to tell cleverly complex parables about humanity.