The more the beam width increases, the softer the shadow.
The intensity of the light is diminished and the color temperature is sometimes affected when the light beam is scattered.
Opal frost is a popular light diffuser--there's a slight softening of the light, without affecting the crispness (it's often used for softening spotlight beam edges without changing the shape of the beam).
There's a 1/2-stop loss of light when using an Opal Frost gel.