I have both the Zaquencer and BSP- they really are different from each other. To me, it's way easier to see what's going on with the BSP, I just don't have the same flow with the Zaq. But, it has some features missing from the BSP.
I'm using the BSP pretty much exclusively with CV these days, and though I do have a MIDI to CV module, I'm using it for keyboard input. So, for my personal situation, it's harder to integrate the Zaquencer into my system.
Both are great, but not really interchangable.