I have the SB600 and SB900 both with clip over diffusers. First thing is how much light do they produce? The SB900 is a really powerful flash but has a lot of controls to regulate the light spread before the diffuser is attached.
So the answer initially to your question is yes up to a point. Like everything in photography taking a photo, be it flash or normal, depends on the situation its going to be used under.
If you can afford it the SB900 really takes some beating for brightness-distance and spread. It also comes with coloured inserts for shooting under different lights. I could have adjusted the spread- brilliance-bounce etc etc on the SB900 but I felt that wouldn't give a true idea of what the clip over diffuser can do
Without diffuser
With diffuser
Taken with sb900 absolutely as taken no prior camera or SB900 setup or alteration to either, just resized for here and under flourescent lighting to give some idea. SB900 pointing straight ahead in both cases. Yes If I had used the coloured plastic insert would make a difference, but the idea was just to show the same shot with and without the SB attachment.
if you asked which Nikon SB flashgun to use I am more than happy with the SB900. It has 3 built in flash patterns to choose from to name just a few of the settings including auto adjust for distance. The setting list is far too long to put on here.
Oh by the way I had just cooked some sausages and eggs hence the frying pan, and they tasted just great
Hope this helps
Realspeed