No difference overall. To get from the first eqn to the second all youre doing is dividing both sides by |n|.
The only noticable difference is choosing the unit normal vector in the second case and not necessarily a unit vector in the first case.
As long as your direction of the normal vector is correct, the length doesnt matter so much.
Agreed, and will just add that the second form of the equation r.ñ = D / | n| can be quite useful in that D / | n| is the perpendicular distance from the origin to the plane.
Agreed, and will just add that the second form of the equation r.ñ = D / | n| can be quite useful in that D / | n| is the perpendicular distance from the origin to the plane.