Yes, short words are better. But not always. It depends on what U want to do. Here is a little silliness with self-reference in response to [Diminutive ~ Pic and a Word Challenge #90], which displays a good use of a long word.
Big word for “tiny” fills out
first line of haiku.
Hmmm. Would anybody want a long synonym for “tiny” in a 5-7-5 haiku? Nah.