Most American haiku poets prefer haiku that has some type of punch to it, a kind of point that sticks out. One might call this an "attention grabber." We here in America are very big into grabbing attention. I call this "sharpness" when it is in haiku. In itself it is just a technique, and can result in good as well as inferior haiku. Here is an example of it in a haikiu I wrote:
an expensive coffin
a new life begins
The sharpness here comes from the irony of new life beginning in a coffin. Sharpness often appears in the form of shock, as it does in this haiku. I like this haiku because on the surface it sounds like a platitude, yet it is quite irrational.
Contrasted with the concept of "sharpness" is the opposite idea of "softness." This is when a haiku does not surprise, or shock, and is not pointed. To me, these haiku are much harder to write, because they may be overlooked. Rather than coming at you and grabbing or challenging you, they invite you in. Here is an example:
On a mud cliff
a stream casts
ribbons of light
I saw this happening one day in the woods in Missouri. It was wonderous. I love the contrast between the mud which is heavy, dark, and wet, and the overlay of light that flows effortlessly over the mud.
My ideal is to write "sharp" haiku without resorting to cheap tricks, or shocks whose only purpose is to hook one's attention, and to write "soft" haiku that glow, without being too vague or non-descript.