strictly speaking both direct n 45deg will be diffused. of course omnibounce recommends 45deg due to the way they supposedly made their product. actually direct flash with tissue paper in place will also be diffused. bounce card at whatever funny angle will also provide some diffusion.
most of the time the crux is not how much diffusion u can obtain, but rather how to minimise the supposedly un-asthetic shadow due to flashlight. thats where all the stuff like flash bracket and off shoe flash come in
for effects that really mimic natural lighting, u can try to experiment with your own style of combination of diffusion+offshoe+direct flash