Well both ways take Uke to the ground....
Apart from Uke being able to "counter attack", I understood from the description that
"not being able to break fall" = "not being able to reduce the wrist torsion", hence the possible breaking of it...
The (few) times I practiced kote gaeshi, it was always done the soft form i.e. I could go down to the mat and spin somehow, without any major pain/problems...
Maybe the "hard" form is correct, AND in fact can be ukemi(ed)?
As a beginner, here I am probably asking this question in fact
