Does anyone have a good sense of how the logic board video of a high end Quadra compares with a (good) accelerated Nubus card in performance?

I ask because:

a) Nubus itself is relatively slow, whereas the logic board video of a Quadra is not encumbered by the Nubus architecture;

B) I am wondering whether adding a good Nubus card (e.g., a late Radius Nubus accelerator) to a Quadra for anything other than a second monitor is worthwhile;

c) and thus whether Nubus video cards are best kept for 68030 machines.