when using stofen diffuser, 80% of the light is spread to all directions, 20% of the light will reach the subject directly, so when using it in a indoor situation, some of the lights will bounce back from walls and ceilings, reach the subject and light up the shadow area. so it still create a define shadow on your subject but only shadow areas are much lighter then without using it.
when using stofen at outdoor, there is noting to bounce, it won't give the effects like using it at indoor situation, the flash light is only 20% effective, if shooting very close up, flash still able to manage to emit enough light, but it is basically waste of flash power.
For using bounce cards in indoor, depends on size of bounce card and the angle of the bounce cards being use, when a large bounce card being use , about near to half of the light is directed to the front, since it create a larger light source, it will soften the edges of shadows slightly if subject is close enough.
when a tiny bounce card is being use, the effective way is the point the flash light towards ceiling, the subject will be lighted up with very soft lighting bounce down from ceiling, the tiny bounce card is the direct a small percentage of light directly toward the subject, it will give better colors and sharpness and a tiny catchlight on the subject (if subject is human or animals).
So when using bounce card at outdoor, there is noting to bounce too, bounce card will not able to give same effects as using it at indoor situations.
One thing I notice many photographers pointing their flash head at 45 degree when using bounce card, same like they are using stofen diffuser.
this is very wrong, the flash head is spilling light toward the subjects, if the photographer is shooting human, the direct flash light will spill on the upper part of body of the subject, resulting either overexposed of the face and underexposed on the lower part of the body.
hope this help.