When it comes to writing, I think less really is more.
In the case of editing a story, I think trying to limit the length results in a better story. It forces me to cut out scenes, dialog, etc. that are superfluous in favor of those that are absolutely necessary. The scenes that are left end up getting picked over to make them more efficient.
The result is a story without a lot of filler. It gets to the point quickly and takes less time for my readers (both of them) to get through.
I've heard this sort of thing from a couple of my favorite authors. Roger Zelazny and Larry Niven both had several short stories that they turned into novellas or novels – in a couple of these cases I recall reading that they preferred the short story because it was "tighter" or that it tried to communicate fewer ideas.
I have to say that as a reader, I agree with them.