Understatement is always best. Analogies in writing are like feathers on a snake. The passive voice is to be avoided. Go around the barn at high noon to avoid colloquialisms. Even if a mixed metaphor sings, it should be derailed.
Exaggeration is a billion times worse than understatement.
Don't use a big word where a diminutive one will suffice. Proofread carefully to see if you any words out. Albert D. Spalding, Jr.