The BVision is based on the Permedia2. It's totally outclassed by any supported Radeon, both in terms of available memory and speed*.
However, I do still have a special soft spot for the BVision card. When I first got it, it totally transformed my everyday usage of the A1200, moreso than the PPC card it attached to. Seeing actual hardware accelerated 3D on the machine (even if it is laughable by current standards) was a buzz

*An exception is in the bus transfer speed from the CPU to the video RAM. For an A1200, CPU access to devices on the Mediator1200's PCI backbone is considerably slower than the CPU -> BVision. This may mean that some applications run a bit quicker on the BVision. The only obvious one that springs to mind is CPU-decoded video playback.