I use picasso96 with my A2000 -Cybervision64/3D graphics card, because despite several hours of trying, I could not get CGX4 to work in this config, so I gave up and tried P96, which worked on the first try.
But yes, if you have a cybervisionPPC for a cyberstorm accel (whether PPC or only 68K), you have to use CGX because P96 doesn't have drivers, as someone already posted. And sometimes that can be 'fun' to get working, too bad the P96 guys never had a CybervisionPPC to write drivers for it, doh!
I believe the cybervisionPPC is the fastest of the cybervision graphics cards series but as you can't test P96 with it, there's no way to know if it would be faster with CGX4 or P96.
Not sure if the cybervisionPPC is faster than the PIV, however, I think it's using a bit newer hardware but honestly don't know.
kevin orme
amiga university
www.amigau.com