Your guess is as good as mine *shrugs*
Generally the level of acceleration offered by P96 or CGX is dissapointing. Common 2D hardware operations like stretched blits, colourspace conversion etc. tend to go unutilised. For those features that are used, it's often the case that the overhead of the whole rtg system (specifically how it interfaces to intuition/graphics) sucks a large initial proportion away too. However, it should all still be much faster than AGA ;-)