The Cybervision 64 is the card that has the passthrough. Cybervision 64/3D is a different card in many details inclduign the 3D.
I have had both. The passthrough is a great feature as it allows for using one monitor for all modes. The 64/3d needs two monitors. One monitor for the native modes of the Amiga, the second monitor for the Cybervision 64/3d modes.